KANSAS CITY, Mo. — The majority of the people injured in an apartment fire Friday have been released from hospitals.

Of the 15 people taken to hospitals, the Bureau of Alcohol, Tobacco, Firearms and Explosives said all but four have been released. Two adults and two children were still being treated for their injuries as of Sunday.

Firefighters responded to the Stonegate Meadows Apartments around 12:35 a.m. Friday. By the time they arrived, flames and smoke were already shooting out of the building.

Some people jumped from the second floor to escape. Firefighters rescued other residents from balconies, and even had to pull some from apartment windows to safety.

Investigators said someone started the fire in the stairwell and blocked escape routes for some residents.

“There was so much damage to the stairwell after the fact,” said John Ham, senior investigator with the Bureau of Alcohol, Tobacco, Firearms and Explosives. “When investigators were trying to work the scene, they laid ladders over to where the stairs use to be because the stairways are basically gone.”

On Friday, the agency determined the fire was intentionally set, and it is being investigated as arson.

“The first thing investigators did is determine the area where the fire started and really investigate that area,” Ham said. “So by their expertise, the burn patterns and that sort of thing along with an ATF accelerant detection K9.”

The ATF announced a $5,000 reward for information leading to the identification of the person or people responsible for setting the fire. ATF agents and Kansas City Police Department bomb and arson detectives are following up on the several tips received since the reward was announced Friday.

Anyone with information about the fire can call the TIPS Hotline at 816-474-TIPS or 1-888-ATF-FIRE to give that information to investigators.