An explosion badly damaged an apartment building in suburban Atlanta in the US on Sunday, leaving the three-storey complex unstable and at least one person injured, authorities said. The cause of the explosion was unknown but a local utility received a call from a resident about a strong gas smell shortly before the midday blast, Dunwoody deputy fire chief Melvin Carter said. One person was taken to a hospital with minor injuries. Mr Carter said 90 per cent 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. He said there were reports of two people missing. A helicopter and drone circled above the building as the local Red Cross began canvassing residents to see who might need help to find accommodation. The building and others nearby were evacuated. Residents were told that Monday was the earliest they could return to their homes. Earlier, the Dunwoody Police Department wrote on social media that they received a report of an explosion at Arrive Apartments shortly before 1.30pm. Brandon Winfield, 28, who lives in a building next to the one that collapsed, said he felt lucky that he avoided injury because he had driven by the site minutes before the explosion. “I’m alive. I’m alive,” Mr Winfield said. Eboni Thornton said she was in a moving lorry outside the building when it felt like something fell on top of the vehicle. The whole vehicle shook, Ms Thornton told WSB-TV. She said she was shocked at what she saw when she got out of the lorry. “The leasing office was collapsed on the left side," she said. "The double doors were blown out and I could hear a lady screaming her head off." Ms Thornton said she saw a couple of people bleeding and being carried out of the rubble. Police said they were working with fire officials to determine the cause of the blast in Dunwoody, a suburb just north of Atlanta.