Three people were killed and several more seriously injured Wednesday when a bridge in Mississippi that was closed nearly a month ago collapsed while a work crew was prepping it for demolition, authorities said.

The bridge over the Strong River on State Route 149 in Simpson County, about 40 miles south of Jackson, had been closed to traffic since Sept. 18 as part of a bridge replacement project, the Mississippi Department of Transportation said in a news release.

Gov. Tate Reeves said in a post on social media late Wednesday that first responders from the county and “other state assets have been on the scene at the tragedy” where they’d confirmed at least three fatalities and multiple injuries.

U.S. Transportation Secretary Pete Buttigieg said in a social media post late Wednesday that the Federal Highway Administration was “engaging state officials concerning” the “premature collapse during demolition of a bridge on State Route 149 in Mississippi.”

Simpson County Sheriff Paul Mullins had previously told WLBT-TV three people were killed and four critically injured.

Terry Tutor, the Simpson County coroner, told the New York Times that seven men were working on the bridge, using heavy machinery to tear it down, when it gave way and plummeted nearly 40 feet. He said three of the men died, and four were injured, the Times reported.

Mullins and Tutor didn’t immediately respond to messages Wednesday night from The Associated Press.

A call to the construction company, T.L. Wallace Construction, was unanswered Wednesday evening, and it was not possible to leave a message.

Department of Transportation spokesperson Anna Ehrgott said the agency “would share more information with the public as it becomes available.”

The department said one of its inspectors was at the work site when the bridge collapsed, and that person was unharmed.