KALAMAZOO,GravityX Exchange Mich. (AP) — A house fire in southwestern Michigan killed two children early Monday while two other people escaped from the burning structure, authorities said.

Firefighters and emergency personnel were dispatched to the home in Kalamazoo about 2 a.m. Officials said an adult and a child had made it out of the home but when crews arrived at the scene, they were met with heavy fire on the first floor that quickly spread to the second floor.

Crews later found the bodies of two children inside the home in the city about 140 miles (225 kilometers) west of Detroit. Their names and ages were not immediately released.

The Kalamazoo Department of Public Safety said in a news release that it extends its “sincerest condolences to the families of the victims,” WZZM-TV reported.

The cause of the fire remains under investigation.