Titusville, FL – TITUSVILLE, Fla. –

A buildup of carbon monoxide — not a gas leak — caused by a non-working fan in the kitchen of a Titusville elementary school sent one student and two staff members to a hospital on Tuesday.

Officials said 41 other students at Imperial Estates Elementary School complained of symptoms, but they were cleared by medical personnel.The conditions of the three taken to the hospital were not known.

Fire officials said carbon monoxide was present with the smell of gas, prompting someone to pull a fire alarm.The school was evacuated, and about 640 students were taken to a shaded area and given water as crews inspected the problem, which was originally believed to be a gas leak.

School officials allowed parents to pick up their children early, but bike riders, walkers and bus riders were not released unless their parents picked them up.

Parents were notified of the incident via the school’s rapid notification system, officials said.

No other details have been released.