Omaha, NE- The whiff of gas that wafted through M’s Pub grew stronger by the minute Saturday, as David Christiansen finished eating one of the restaurant’s famous flatbreads known as lahvosh.

His wife, Connie Spencer, thought about saying something to the waitress, but she didn’t have time.

In seconds, she and her husband were knocked to the floor.

Within hours, one of the city’s most beloved restaurants — a landmark that was arguably the heart of the Old Market — was no more. And a historic four-story building located on the busiest corner in the Old Market was gone, entirely engulfed in flames.

It burned out of control until just past midnight.

Smoke, shock and sorrow permeated downtown Omaha.

“It is so sad. It is so iconic,” said Gena Dushan, one of the people who gathered to watch the tragedy unfold in the bitter cold.

Fire Chief Bernie Kanger said early Sunday that “the fire for all practical purposes is out.” He said firefighters had started to scale back but were focused on hot spots — one flared about 6 a.m. this morning on the second floor.

Firefighters doused the building throughout the night with four fire hoses, scaling back to three at about 5:30 a.m. All of the windows of the building were gone, and the four-story brick building was now a ghost of itself, encased in frost and icicles.

A city plow waited nearby, presumably to begin work on the streets in the center of the Old Market that were capped with about an inch to 2 inches of ice. Streets on all four sides of the building were closed within a block.

Kanger said crews hoped to be able to enter the building at first light to assess damage and integrity of the building.

The one bright note in the day was that no one was killed. One man was seriously injured and taken to the Nebraska Medical Center, Kanger said.

M’s Pub just celebrated its 43rd birthday. It was the oldest restaurant in the Old Market area and the site of many first dates and anniversary celebrations.

Its death began at 2:51 p.m., when an explosion rocked it and surrounding buildings.

Firefighters battled for hours to save the building in the bitter cold, but for much of the evening, the fire appeared to get the upper hand. About 8:40 p.m., flames were seen roaring with abandon out of the roof, and firefighters began to issue warnings that adjoining buildings housing restaurants such as Stokes were at risk.

Kanger noted that the wood floors and the wood bar that made M’s Pub a perfect place to spend a winter’s afternoon made for a quick-burning fire. He also said the extreme cold was creating mechanical problems with the firefighting equipment. The temperature hovered around zero in late evening. Many of the firefighters took breaks in a nearby hotel lobby to get warm.

Besides all the combustible wood in the building, Kanger said there were also a lot of open spaces that allowed the fire to spread quickly to higher floors.

The fire chief declined to speculate about what caused the fire, but numerous witnesses, waiters and diners all said that they smelled gas shortly before the explosion, and that they saw flames shooting upward 5 to 6 feet outside M’s patio.

They also said a company had been working outside M’s Pub for several days, drilling and excavating. Nearby there were rolls of what appeared to be fiber optic cable.

Scott Sasser, a longtime waiter at M’s Pub, also said he and others had smelled the strong odor of natural gas shortly before the explosion. A waitress went outside to check to see where it was coming from.

Sasser said he believes — although he does not know for sure — that the workers digging outside the restaurant had hit a gas line.

“I think everybody is just in shock. It’s pretty bad. Everything is fixable. The most important aspect is that no one got seriously hurt, and people could have been killed,” Sasser said.

Many people in the Old Market reported smelling gas. Even people two blocks away said they smelled gas and called 911.

Rich Bronner was smoking a cigarette on the corner of 11th and Harney — about a half block away — when he heard the explosion.

He said there were several workers outside the restaurant, and as soon as they heard the boom, one worker “threw his hands up in the air” and began to run.

Tracey Christensen, a spokeswoman for the Metropolitan Utilities District, said it was not clear whether the explosion was caused by a natural gas leak. She said the utility was working with the Omaha Fire Department and the State Fire Marshal’s Office to determine the cause.

MUD turned off the gas to the building at 4:30 p.m. And, as a precaution, they searched for a gas leak in the area but found nothing, Christensen said.

They did not have any crews working in the area at the time of the explosion, Christensen said.

Chief Kanger said Saturday evening that he could confirm only that there was a report of a possible explosion that preceded the fire. He said he couldn’t identify the origin of the fire, saying that was under investigation.

At M’s Pub, the word was given for the cooks in the basement to shut everything down and to come upstairs to the restaurant.

“We started evacuating right before it happened. One of our cooks — on the back stairwell that blew up — was hurt,” said Sasser, who had worked at the restaurant for nine years and who is known as “Scottie.”

“I was in there when the windows blew out, it was just surreal,” said Sasser, who was shocked and shaken about an hour after the explosion.

Spencer and Christiansen — the Council Bluffs couple dining on lahvosh — said everybody in the building exited through a side door. “When we came out, people were still in shock. One woman was screaming, ‘Where is my daughter? I can’t find my daughter!’ ” said Spencer.

Authorities say everyone was evacuated from the building, including the 14 condo units above and next to M’s Pub. At least 12 people were living in those condos, including Mark and Vera Mercer.

The Mercers owned the building that housed M’s Pub, along with Nouvelle Eve. They also owned the part of the next-door building that houses The Market House. During the fire, the Mercers were spotted at their nearby restaurant, La Buvette. However, they declined to comment.

One of the condo dwellers, Marilyn Tourtellot, lived on the fourth floor. She was upstairs in her bedroom area when she heard the explosion and looked out the window.

“It almost knocked me out of the chair. And I went right to the front window and saw all the people running out of M’s and all the workers running across the street,” said Tourtellot, an interior designer who has lived in the Old Market for more than 10 years.

Tourtellot said there had been people working in the area for several days with big machinery. “My neighbors across the hall came over and got me and we all came down the stairs. As we walked out, we could see huge flames coming out of the basement of M’s,” said Tourtellot.

Police and firefighters were on the scene in minutes. They quickly evacuated nearby buildings, including the Old Market restaurants and adjoining condos.

Nick Bartholomew, co-owner of The Market House, said he too believed the explosion occurred in the basement area. The Market House is a new restaurant in Omaha. Its basement is connected to the basement for M’s.

Initially, one of the owners of M’s Pub — Ron Samuelson — vowed to rebuild. But that was earlier in the afternoon, before the fire raged on and the floor, along with a wall in the restaurant, had collapsed.

Several hours later, Samuelson said he was “overwhelmed” by the devastation. His main worry was his employees, many of whom had worked at the restaurant for years.

“It wasn’t just waiting tables, it was waiting tables at M’s Pub,” said Samuelson, who was in Phoenix and learned about the explosion when a friend texted him and asked if there was anything he could do to help.

He was, however, thankful that no one died.

“From the looks of it, I can’t believe that someone wasn’t more seriously hurt,” said Samuelson. “It just looks horrible.”

As for the couple who dined at M’s on lahvosh and a chicken sandwich, they’re just glad they got one last meal at the restaurant, and they made it out without a scratch.

“I have mixed emotions. I’m glad we were one of the last customers, but I hope they rebuild. It was such a landmark in Omaha,” said Christiansen.

In January 2013, M’s Pub celebrated its 40th birthday. It was a year older than Spaghetti Works, which opened in 1973, and older than V. Mertz, which opened in 1975. It was popular with tourists and also Omahans, who would sip wine on its patios during hot summer days.

It always had an urban feel. Its tables were close together, and it attracted a diverse group of people, many of whom were regulars at the bar. Some of the most famous patrons of M’s Pub were known as the Slime Dogs — a group of longtime friends who spent Friday nights at the end of the bar.