Lake Mead, NV – A dozen people are recovering from carbon monoxide poisoning symptoms they experienced Sunday morning while on a boat at Lake Mead.

Five people were airlifted to UMC for treatment while four more were treated after being transported by ground to an area hospital. Three more were treated and released.

“They had signs of carbon monoxide poisoning in their systems,” said Christie Vanover, spokeswoman for the recreation area. “The call came in on Marine radio about 8:30 a.m. I understand all have been released from the hospital as of this afternoon. We think the problem came from a generator on the boat.”

About 12:20 p.m., a boat with two people onboard caught fire but was extinguished without injuries, Vanover said.