Napier Fire Service senior station officer Mark McGill said they isolated the line and the gas company fixed the problem.
People were evacuated about 150m either side of where the leak was located outside Galvanising Hawke's Bay Limited.
"It went quite smoothly. We evacuated and we put a water curtain on it to suppress the gas."
One worker at nearby Tumu ITM Napier said the situation had been "quite scary", given the loud hissing noise that could be heard.
However, Tumu business partner Paul Waite said all 25 staff were evacuated quickly and had returned to work within half an hour.
"I think we were disrupted for about half an hour. It looked like the emergency services were doing a great job. There was definitely the smell of gas."
Staff were advised to evacuate after being informed of the leak by staff from neighbouring business Galvanising HB.
"The local business community seemed to rally together and fire and police were here pretty quickly."
A constant stream of customers had to be turned away but there was no real effect on business.
Galvanising HB general manager Richard Millea said the leak had come from a mains gas line after a flange blew.
"Because it's a large mains that supplies our site the gas leak was quite significant. It was a high-pressure leak, so we immediately evacuated the site and contacted the fire brigade and the gas company.
'It was a major leak. It was a big main that blew, it's actually [(the gas company's] service main."
Millea said about 15 people had been evacuated without issue and fire trucks were on the scene promptly. Gas contractors shut down the gas about 30 minutes later.
Millea also said the gas company had also been able to restore gas supply just in time to get the company back to business.
"We have a zinc pot here that we use for galvanising, it's molten zinc and the zinc would have rapidly hardened without the gas burners, which would mean we would lose production for days without it."
Powerco gas operations manager Don Elers said field staff isolated the leak, which was found to not be on Powerco's network, by about 2.30pm.
"The leak was found to be on a gas meter set, which measures gas for the customer, at Galvanising Hawkes Bay. While the equipment was not on our network to fix, we isolated it to make it safe."
Emergency services were again in action when they were called to the scene of a rolled logging truck and trailer at 3.45pm.
The NZ Fire Service attended. A crew from Hastings deployed absorbent material to mop up a diesel spill from the rollover, which happened at Bridge 3 on State Highway 50.
The driver was treated at the scene and taken to hospital. No other vehicles or passengers were involved.
A St John ambulance spokeswoman confirmed a male patient of unknown age was taken to Hawke's Bay hospital with moderate injuries.