The Whittaker's chocolate factory has been evacuated after a high-pressure gas main ruptured in Porirua.

The Porirua Fire Service was called to the the burst main about 4pm on Monday, and used cutting equipment for rescuing people from cars to crush the pipe to reduce the pressure.

Fire shift manager Belinda Beets said the the area was evacuated while crews waited for the gas company, Powerco, to arrive.

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"They've closed as much of the pipe as they can to reduce the amount of gas leaking," she said.

The area was industrial, so no homes had to be evacuated.

The Whittaker's chocolate factory is in Mohuia Cres, Porirua. The company could not be reached for comment.

About 6pm, Powerco gas operations manager Don Elers said the gas leak had been contained. While the gas service line did not supply Whittaker's, the factory was evacuated as a precaution.

It was unknown how many properties the damaged service line supplied, and repairs would be carried out on Tuesday.

An investigation would be undertaken over the next few weeks.