One construction worker was killed and another critically injured in a Cambridge parking garage after the stairwell they were working in collapsed the morning of March 3.

The two workers, both men, had been removing a stairwell, which was to be replaced, when a section of it collapsed, Gerard Mahoney, the city's acting fire chief, told reporters.

Cambridge firefighters, as well as EMTs and police, rushed to the garage at 8:23 a.m. in response to a “stairwell collapse,” the department noted on its twitter page.

Roughly a ton of concrete and steel came raining down in the accident, which took place on the second floor, Mahoney said.

The deadly accident at the city-owned garage in East Cambridge comes just a week after two construction workers were killed in downtown Boston doing emergency repair work on High Street for the city’s water and sewer commission.

The surviving worker in the Cambridge accident was transported to a nearby hospital after suffering a serious chest and arm injury, according to Mahoney.

The contractor overseeing the work at the First Street Garage, located near the CambridgeSide mall, is Structural Preservation Systems, but the two men were working for an unidentified subcontractor to the firm. Michael Biesiada, head of sales and marketing for Structural, declined to name the subcontractor or the type of work it was doing. 

“There is not a lot I can tell you about what happened,” said Biesiada, adding that the company is awaiting the results of the investigation.  

The company, which lists a Cheshire, Conn., address, submitted the winning bid for repair work on the 1,100-space garage last September. Structural Preservation bid just under $1.5 million for the job of shoring up the First Street Garage, beating out two Quincy-based competitors, according to city records.

The U.S. Occupational and Safety Health Administration is investigating the accident. Middlesex District Attorney Marian T. Ryan’s office is looking into it as well.

Trenching Accident

In the Boston accident, two men were killed when a truck pushed them into a deep work trench in the street. The workers were identified by The Boston Globe as Jordan Romero, 27, and Juan Carlos Figueroa Gutierrez, 33. They had been repairing a clogged sewer line for a nearby office building.

That accident, in turn, has raised concerns about how thorough Boston officials were in vetting the contractor on the job, Atlantic Coast Utilities.

The owner of the company, Laurence M. Moloney, signed a pair of city affidavits stating his firm had not been investigated by OSHA in the previous five years, the Globe reported.

But OSHA had cited his company twice during that time period for workplace safety violations, according to the Globe.