CAMBRIDGE — One worker was killed and a second was critically injured in Cambridge Wednesday when a section of concrete stairwell inside a city-owned parking garage collapsed during renovation work.

A 56-year-old man was pronounced dead at the scene, officials said. A second worker, a 41-year-old man, suffered a “significant chest injury” and was listed in critical condition at a hospital.

“Our hearts go out to the families and friends of the workers,” said Mayor Sumbul Siddiqui. “It’s really an unfortunate set of circumstances, especially on the heels of what happened in Boston.”

The collapse occurred one week after two workers repairing a sewer line were killed at a construction site in Boston’s Financial District after a truck knocked them into an excavated ditch in the street.

In Cambridge, the workers were employed by a subcontractor renovating a stairwell at First Street Garage, according to the city’s acting fire chief, Gerard Mahoney.

They were the only people in a second-floor stairwell when the concrete gave way around 8:20 a.m., Mahoney said at a news conference.

Officials did not identify the workers. The Middlesex district attorney’s office is investigating.

A spokesman for Structural Preservation Systems LLC, the general contractor to renovate the garage, said he didn’t know the name of the subcontractor who employed the workers. The company, a national firm with offices in Massachusetts and Connecticut, is investigating, he said.

“We’re deeply saddened,” said Mike Biesiada, the spokesman. “Our focus is on investigating what was the root cause of this incident.”

The company was awarded a contract for the project in September after it submitted the lowest bid at just under $1.5 million, city records show. The staircase, which has windows open to the weather, was closed about a month ago but the garage remained open.

Shanaj Hussein, who had parked her car nearby, said she “saw something fall,” followed by a cloud of dust. She saw a man on the floor and called 911. There were “two guys running around,” she said. “I was shaking.”

US Occupational Safety and Health Administration investigators and structural engineers arrived at the garage as emergency responders prepared to leave.

OHSA’s website shows the agency has inspected Structural Preservation Systems 10 times since 2010. Seven of the inspections found no violations.

In 2016, OSHA initially cited the company for a serious violation and proposed a $5,000 penalty, which Structural Preservation Systems contested. The company and OSHA later agreed to a settlement, and both the citation and penalty were dropped, the agency said.

In two other inspections that found violations one citation was upheld through a settlement, the agency said. The citation was considered an “other than serious violation” and didn’t result in a financial penalty, OHSA said.

There are two other major construction projects taking place in the East Cambridge neighborhood where the collapse occurred, and many workers took time to stop by the garage.

Gineton Silva, who works at a nearby construction site, said that while what happened was tragic, it doesn’t make him more fearful. “Things happen. You can’t be scared all the time,” he said.

Still, it was unnerving to hear about someone getting killed on the job.

“It’s crazy,” he said. “It’s very sad whenever someone dies.”

Another construction worker, Benjamin Ramirez, said he wasn’t frightened by the collapse but that it would make him more cautious when working.

“Honestly the first thing I thought of was our stairwell collapsing,” Ramirez said. “I wouldn’t want to be one of those guys.”

In a statement, the Massachusetts Coalition for Occupational Safety and Health said the job-site deaths in Cambridge and Boston account for three of four construction-related fatalities this year in Massachusetts. The first death was Jan. 3 when a handyman fell from a ladder in Chelsea, the group said.

Last week, Jordan Romero, 27, and Juan Carlos Figueroa Gutierrez, 33, were killed while working for Atlantic Coast Utilities on High Street in Boston, where owner Laurence M. Moloney’s company was hired by a private landlord to fix a plugged sewer line.

The men’s deaths have raised questions about the city’s oversight of construction companies in Boston, since it appears Moloney erroneously reported in two affidavits that he had not been investigated by OSHA in five years.

OSHA records show the company was found to have violated workplace safety rules in 2016 and 2019.

Following a 2016 South End trench collapse that killed two workers at a construction site, Boston enacted an ordinance requiring that individuals or businesses receiving work permits in the city report their safety record — current or unresolved — including any OSHA violations.

Previously, the city did not have the authority to require that history and was not notified of OSHA violations.

But last week’s deaths raise questions about the effectiveness of that measure. During a virtual meeting on Wednesday, City Councilor Michael Flaherty said it was clear that Boston should strengthen its construction regulations.

“Specifically for companies that get cute and fail to mention or they omit, be it intentionally or accidentally, their prior track record, there should be a penalty for that,” he said.

Flaherty proposed a multiyear or lifetime ban on doing business in the city for companies that fail to disclose previous workplace violations.

Danny McDonald, John R. Ellement, and Travis Andersen of the Globe staff contributed to this report.

Laura Crimaldi can be reached at laura.crimaldi@globe.com. Follow her on Twitter @lauracrimaldi. Tim Logan can be reached at timothy.logan@globe.com. Follow him on Twitter at @bytimlogan. Charlie McKenna can be reached at charlie.mckenna@globe.com.