BOULDER, Colo. -- An apartment complex that caught fire Saturday night has been deemed uninhabitable because crews have found asbestos in the drywall.

Residents will not be allowed into the building until state inspectors have an opportunity to test the air quality, said Sarah Huntley, spokeswoman for the Boulder Fire Department.

The inspection is expected to take about a day.

"The only things I have are the clothes on my back," said Kevin Henry, who lived on the third floor.

Most of the residents spent Sunday afternoon meeting with the apartment manager and an environmental team who warned them almost everything could be a complete loss.

"Asbestos gets into the fibers of things and can be pretty timely and expensive to clean," said Henry.

The American Red Cross opened a service center for residents at the recreation center at the University of Colorado. About 50 people were displaced by the fire, Huntley said.

The fire started at about 5:15 p.m. Saturday. More than 50 firefighters were on scene.

Firefighters stayed at the complex throughout the night to make sure the fire did not re-ignite, Huntley said.

None of the residents were injured but Huntley said one firefighter was treated for a minor shoulder injury and heat exhaustion.

Investigators are not releasing an official cause of the fire, but they say it appears the blaze was started accidentally. They have ruled out the possibility of fireworks or any kind of barbecue grill, Huntley said.

Witnesses said the fire started on a balcony, but quickly spread.

"From the front it was smoking," said Peter Jentsch who shot video of the fire. "But from the back you could see the flames from multiple areas of the house."