About 2 million gallons of raw sewage have spilled into Nantucket Harbor since a main sewer line failed on the island during Thursday’s major winter storm, officials said.

Repairs to the 20-inch diameter sewer line that runs beneath South Beach Street were hampered by the extreme cold Saturday, said Roberto Santamaria, director of public health on Nantucket.

At least 24 workers braved temperatures in the teens and a sub-zero windchill factor to work to repair the pipe throughout Saturday.

Both the US Coast Guard and the National Guard assisted to deliver extra crews and parts to repair the pipe, after the icy waters of Nantucket Sound canceled some ferry service.

A National Guard helicopter flew workers from a Cape Cod-based contractor to help with repairs. The Coast Guard used an ice-cutter to clear a path for a ferry to depart Hyannis Harbor to deliver pipes, valves, and other equipment, Santamaria said.

By Saturday night, crews had installed a pipe to bypass the break, diverting the sewage to the north of the ferry dock, “where the tide will allow it to flush out,’’ Santamaria said by telephone Saturday night.

The effect on marine life in the harbor is expected to be minimal, he said.

“A lot of the wildlife that’s in the harbor is either dormant or a lot of them have already migrated away from the area,’’ Santamaria said.

Still, the spill prompted the state Division of Marine Fisheries to temporarily halt shell fishing in waters around the island, Santamaria said.

Nantucket officials are working with state and federal environmental agencies on plans to remediate any damage caused by the spill, he said.

A spokesman for the state DEP said the agency is closely monitoring the spill.

“It’s obviously a serious spill. We’re taking it seriously, [and] we’re working with the local community officials to make sure it gets addressed as quickly as possible,’’ spokesman Ed Coletta said.

Santamaria said crews are working to contain the environmental effects.

Solid waste was being screened out of the sewage flowing into the harbor, he said. It is unclear how long it will take to repair the pipe.

“It could be a few days,’’ Santamaria said.

Sewer service for residents has not been affected, he said.

The break caused untreated sewage to bubble up onto the streets near the center of town. A handful of restaurants closed because of concerns about public health, he said.

They will remain closed until the area is decontaminated and engineers have determined that the street and sidewalks are structurally sound, Santamaria said.

Jacob Carozza can be reached at jacob.carozza@globe.com.