An explosion rocked an apartment building in suburban Atlanta on Sunday, rendering the three-story complex unstable and leaving at least one person injured, authorities said.

Dunwoody Deputy Fire Chief Melvin Carter said the cause of the explosion was unknown but that Atlanta Gas had received a call from a resident of a strong odor shortly before the mid-afternoon blast. One person with minor injuries was taken to a hospital for treatment.

Carter said 90% of the building had been searched and that officials were in the process of shoring up the rest of the complex so that rescuers could continue searching for anyone who might be trapped inside. He said there were reports of two people being unaccounted for.

Photos from the scene show part of a building collapsed into heaps.

The Dunwoody Police Department wrote on social media that they received a report of an explosion at Arrive Apartments shortly before 1:30 p.m. Photos from the scene show part of a building collapsed into heaps.

“This is a very active scene and the cause of the explosion is under investigation,” police wrote.

Eboni Thornton told WSB-TV that she was in a moving truck outside the building when it felt like something fell on top of the vehicle. She said the whole vehicle shook. She was shocked at what she saw when she got out of the truck.

“The leasing office was collapsed on the left side, the double doors were blown out and I could hear a lady screaming her head off,” Thornton said.

Thornton said she saw a couple people limping and bleeding and being carried out of the rubble.

Police said they are working with fire departments to determine the cause of the blast. They asked complex residents not impacted by the explosion to remain in their apartments.

Dunwoody is a suburb just north of Atlanta.