CLARKSVILLE, Tenn. - Five bikers were found dead Sunday in a recreational vehicle at a Tennessee speedway and a festival organizer said fumes from a generator were to blame.

Three men and two women were found in the RV at the Clarksville Speedway about noon and there was no sign of foul play, Clarksville police spokesman Jim Knoll said.

The head of Bikers Who Care, the charity that organized the event, said he heard someone shouting that all of the people in the trailer were dead. The event festivities came to an abrupt halt as ambulances arrived.

"This is a tragic accident," Bill Langford said. "It's horrible."

Langford said the bikers' group was like a close-knit family and he knew the people who had died. He identified them as a married couple who had 8-month-old twins. He was a truck driver and she was a school teacher.

The others who died were another couple and a man who worked with one of the men. All were from the Clarksville area about 40 miles northwest of Nashville.

Two of the men worked security on Saturday night during the event's big party, which featured motorcycle drag races, live music and fireworks. Bikini and tattoo contests were scheduled and the charity's website said there was free beer.

Langford said it appears a small storage hatch on the RV did not close properly, allowing fumes from the generator to leak inside the vehicle.

The bikers who found the bodies were taken to a hospital after feeling dizzy and light-headed, Langford said. They all had high amounts of carbon monoxide in their systems, he said.

Photos from the festival showed yellow police tape around the camper and tents that had been put up nearby.

Langford said the event collected toys for needy children and raised funds for Camp Rainbow, a summer camp for seriously ill children at Land Between the Lakes recreation area on the Kentucky-Tennessee border. They also help the Buddy Ball sports league for children with mental and physical disabilities.