Concern spread across the city of Davenport, Iowa as part of a historic six-story apartment building collapsed Sunday, followed by the rescue of seven people, while others were left injured, officials informed.
As a secondary search of the property was underway Sunday night, local officials stated at a news conference that they were still worried over the possibility that some might be buried in the rubble, reported NBC News.
According to Davenport Fire Chief Mike Carlsten, the collapse just before 5pm may have resulted in a significant natural gas leak and water leaks from each floor, the report said.
"A portion of the rear building had actually collapsed, separated from the building," he said.
He also added that during the rescue operation, seven people were rescued, while more than a dozen people were helped by first responders as they left the building.
"So far, all had been treated on-site," Carlsten said, underlining relatively minor injuries.
"There are people unaccounted for," Mayor Mike Matson said, indicating the possibility of unknown deaths.
According to Matson, the reason for the collapse was being investigated and building inspection by city structural experts was anticipated.
He also said that he was not sure if the residents who were evacuated and received assistance from the Red Cross would be able to return.
"We're not actually sure how stable the building is," Carlsten said.
"Even while we are on scene we did have multiple secondary drops of debris coming from that structure," he added.
Based on the information available at the city's public library, the building is "constructed of brick over steel and concrete."
The property had "permit issues" for the outside brickwork, according to Rich Oswald, the city's director of development and neighbourhood services.
He added that the city had ordered the owners to carry out a number of modifications and repairs.
Furthermore, he said that the complaints of bricks falling recently were connected to that job. Officials admitted during the news conference that the condition of the building in downtown Davenport was the "subject of several resident concerns."
"The tenants of this building are pretty active," Oswald said. "They've called the city numerous times with complaints."
The building's ownership was not immediately clear. According to city records, organisations referred to as the Davenport Project and the 324 Main Street Project have long-planned upgrades to the structure while pursuing "tax breaks."
The Davenport Hotel, one of the best hotels in the city at the time, was housed in the structure, located in the Cork Hill neighbourhood when it was finished in 1907. The building is also listed on the National Register of Historic Places.