Four people are dead, five injured and four unaccounted after a plane crash in Wichita, Kansas, Thursday, CNN reported. The small plane lost an engine shortly after takeoff and crashed into a two-story building at the Mid-Continent Airport.

Officials believe about 100 people were in the FlightSafety International building when the plane hit, Wichita Fire Chief Ron Blackwell told KSN-TV. Walls and ceilings collapsed, at one point making the building too dangerous to search, the Associated Press reported. Firefighters have also evacuated.

Of the injured people, three have serious injuries. They were all transported to hospitals, according to a statement from the airport. The twin-engine Beechcraft King Air 200 plane was trying to return to the runway when it crashed at about 9:50 a.m. Central Time, KSN-TV reported.

“The airport crews arrived first, seeing smoke and flames and what appears to be a plane striking the building," Blackwell said in a press conference. "Firefighters engaged in a horrific fight for several minutes. We have the fire under control. We are in the process of trying to determine if all the employees and visitors who may have been in the building are accounted for."

Both the Federal Aviation Association and National Transportation Safety Board have been alerted. The FBI, Kansas Highway Patrol and Mid-Continent Public Safety Department were among the agencies that responded, according to the airport's statement.

Mid-Continent flights were mostly on schedule, but passengers were advised to check with their airlines about possible delays.