A Thunder Bay sewer and water crew caused the natural gas leak that forced Thursday's evacuation of a north-side neighbourhood.

The general manager of infrastructure and operations in Thunder Bay, Darrell Matson, said the crew was repairing a damaged catch basin at Red River Road and Rupert Street.

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Thunder Bay manager of operations and infrastructure, Darrell Matson (CBC)

"As a result of those repairs, a rubber-tired backhoe came in contact with a gas line, which caused a rupture," Matson said.

City crews typically deterimine the location of underground services before excavation begins, but Matson said there are a number of things that might have gone wrong.

"[Either] the locates were in the wrong locations, or ...somebody got too close to one of the mains," Matson said. "So in this case, that is under investigation."

The province's Technical Standards and Safety Authority, the Ministry of Labour, and Thunder Bay's health and safety department are also looking into the incident.

Matson said no work will be done at the scene by city workers until the investigations are complete.

Meanwhile, barricades remained up on Red River Road Friday morning, although local traffic was being allowed in.

A Union Gas spokesperson said traffic with continue to be disrupted until the clean up is finished. The company completed repairs to the damaged pipe last night, just before 11 pm.