DUNWOODY, Ga. (AP) — An explosion rocked an apartment building in suburban Atlanta on Sunday, causing the three-story structure to partially collapse and leaving four people with minor injuries, authorities said.

The cause of the explosion was unknown, but a local utility had received a call from a resident about a strong odor of gas shortly before the midday blast, according to DeKalb County Fire and Rescue Deputy Fire Chief Melvin Carter. He said 90% of the building had been searched and officials were in the process of shoring up the rest of the complex so rescuers could continue searching for anyone who might be trapped.

Captain Jaeson Daniels said two people were unaccounted for and may have been in one of three apartments that had completely collapsed. Rescuers haven’t been able to enter those apartments due to instability of the overall structure.

“We are attempting to look for those two unaccounted for people,” he said. “Those people may not have been here when the explosion happened.”

A helicopter and drones circled above the structure as the local Red Cross began canvassing residents to see who might need help finding accommodations. The partially collapsed building and several others nearby were evacuated. Residents were told that Monday was the earliest they could return to their homes.

Brandon Winfield, 28, who lives in a building next to the one that collapsed, said he felt lucky that he avoided injury since he had driven by the site minutes before the explosion. The collapse reminded him of a terrible accident that happened when he was a teenager, severing his spinal cord while participating in motocross.

“I’m alive. I’m alive,” he said. “I’ve dodged two bullets.”

Chantel Jefferson, a 21-year-old Amazon driver, had parked her van directly outside the building and was gathering packages to take inside when she heard a “huge explosion” and trees and debris began falling on her vehicle. People came running out of the building, screaming and bleeding from their injuries.

“I was just inches away from it. I would have gotten blown up,” she said. “I just happy I didn’t make it in there.”