Updated 12:55 p.m. Sunday

A construction worker who was hit by a steel beam at the Twin Peaks Tunnel Project died on Friday.

Patrick Ricketts, a 51-year-old signal technician, was pinned underneath the beam at about 4:30 p.m. on Friday. According to the San Francisco Municipal Transportation Agency, nearby workers rushed to help Ricketts, who was transported to San Francisco General Hospital, where he died later that evening. Ricketts lived in the Colusa County town of Williams, 100 miles north of San Francisco.

MTA spokeswoman Erica Kato says Ricketts was employed by Oakland-based Shimmick Construction. Shimmick did not respond to a request for comment.

Work on the tunnel was suspended pending an investigation by San Francisco police and Cal/OSHA. The SFMTA said late Saturday that crews were cleared to resume work.

“We have taken extra precaution to ensure the tunnel is safe before returning workers to the project,” said SFMTA director Ed Reiskin in a statement. “We feel confident that the contractor, under the SFMTA’s oversight, has done everything possible to ensure construction can proceed safely.”

Mayor London Breed released a statement Friday with condolences to the worker's family, friends and colleagues.

"This is a tragic incident and I want to commend the Twin Peaks Tunnel laborers who quickly sprang into action to help their colleague," Breed said.

The retrofitting project is replacing tracks and drainage systems in the tunnel, which connects the city's West Portal neighborhood to downtown San Francisco.

Bianca Hernandez and Queena Kim contributed to this story, which also contains reporting from The Associated Press and Bay City News.