OMAHA, Neb. (AP) — Authorities are investigating the deaths of two people in a house fire in Omaha.

Crews were called to the fire just before 3 a.m. Saturday, the Omaha Fire Department said in a statement. Smoke and flames were visible from a block away.

The blaze was extinguished in about 30 minutes despite difficulties caused by the collapse of stairs and partial collapse of the main floor, the statement said. Two people were found dead inside. Their names were not immediately released. No other injuries were reported.

The two-story house was deemed a total loss. The cause of the fire remains under investigation.

Battalion Chief Matt Carmichael told KETV-TV that firefighters initially believed the structure was vacant and focused on the outside of the home before going in. Once inside, they found two people they believed were homeless.