A portion of a historic six-story apartment building in Davenport, Iowa, collapsed Sunday, leading to the rescue of seven people and injuring an unknown number of people, authorities said.

Concern that some could be buried in the rubble lingered Sunday night as a secondary search was conducted on the property, city officials said at a news conference.

The collapse just before 5 pm may have caused a large natural gas and water leak from each floor, Davenport Fire Department Chief Mike Carlsten said during the conference call.

«A part of the rear building had actually collapsed, detached from the building,» he said.

Onlookers watch as emergency crews work at the scene of a partial building collapse Sunday on Main Street in Davenport, Iowa.
Onlookers watch as emergency crews work at the scene of a partial building collapse Sunday on Main Street in Davenport, Iowa. Nikos Frazier/AP

In addition to seven rescues, first responders helped more than a dozen people as they exited the building, he said. So far, all have been treated at the scene, Carlsten said, indicating relatively minor injuries.

But authorities did not rule out possible deaths. «There are people missing,» Mayor Mike Matson said.

The cause of the collapse was under investigation. City structural experts were expected to examine the building, the mayor said. It is not clear if the residents, who were evacuated and helped by the Red Cross, will be able to return.

«Actually, we’re not sure how stable the building is,» Carlsten said. «Even while we were on the scene, we had multiple secondary drops of debris coming from that structure.»

the building is built of brick on steel and concrete, According to the city’s public library.

Rich Oswald, the city’s director of development and neighborhood services, said property owners had «permitting issues» for the exterior brick work. In addition, he said, the owners were under orders from the city to make specific repairs and improvements, he said.

Reports of falling bricks in recent days were related to that work, he said. The condition of the building in downtown Davenport was the subject of numerous complaints from residents, officials acknowledged at the news conference.

«The tenants in this building are quite active,» Oswald said. «They have called the city numerous times with complaints.»

Ownership of the building could not be immediately determined. city ​​documents show that the entities he called the 324 Main Street Project and the Davenport Project have long planned improvements to the building while seeking tax breaks.

The building, in the Cork Hill district, was completed in 1907 and housed the Davenport Hotel, the best accommodation in the city at the time. The building is listed in the National Register of Historic Places.

Michelle Acevedo and Tavleen Tarrant contributed.