Quick-thinking petrol station staff averted potential disaster in Hamilton yesterday when a man sprayed petrol across their forecourt and put a match to it.

The man acted without warning at the Z Energy station opposite the courthouse on Anglesea St about 1.30pm.

Police were last night hunting the arsonist, described as a 182cm tall, athletic male Maori wearing a white hooded sweatshirt underneath a black vest with white, green and grey camo-style long trousers.

He walked onto the forecourt where he lifted a pump nozzle, placed it on the ground and poured out 10 litres of petrol, then put a flame to it.

Three petrol pumps were in flames for a time, closing the service station.

Hamilton man David Luke was driving past the service station when he saw smoke and stopped to help.

"I parked my car outside the courthouse and went across the road to help," he said. "I grabbed an extinguisher and helped a forecourt attendant to put the fire out."

Mr Luke said he did not see the man responsible but hoped he would be caught soon.

"It was natural instinct for me to stop and help - it wasn't a good situation."

Hamilton Central senior station fire officer Alban Osborne responded to the emergency call but when they arrived staff had put out the fire and secured the situation.

"It's certainly a very dangerous act," Mr Osborne said.

"If there were cars on the forecourt, and that fuel has gone around the vehicles, and who knows it could have been young children in the cars, there was potential for serious harm.

"With any fuel fire, the fuel runs across the ground - it can enter drains, stormwater and spread underground."

There was also a small chance of the fuel tanks igniting, he said. However, none of that eventuated thanks to the quick response from staff. They immediately disabled the pumps and doused the flames with dry powder extinguishers.

"It was excellent work by staff - because of their quick actions they saved a lot of damage," Mr Osborne said.

Police have viewed CCTV footage of the incident but declined to release the footage to media.

Z Energy communications adviser Sheena Thomas said all staff were trained for such situations.

"They see it as something they just had to deal with."

Police are seeking witnesses to the incident, including any sightings of the offender who fled the scene on foot. He was last seen running south on Anglesea St and into Clarence St.

Anyone with information should contact Detective Constable Colin McCracken of Hamilton on (07) 858 6200 or Crime Stoppers on 0800 555 111.

- © Fairfax NZ News