Police are investigating a suspected arson attack following a fire at a packed gay club on New Year’s Day in the US city of Seattle.

The Seattle Times reports an individual was seen pouring petrol shortly after midnight on Tuesday on a stairway at Neighbours, which bills itself as the city’s largest and longest-running gay club.

Situated in the Capitol Hill area, about 750 people were in the club at the time of the incident.

No injuries have been reported.

The fire was quickly put out by a nightclub patron who grabbed a fire extinguisher. Carpet in the venue had been set alight.

The activation of the club’s sprinkler system, a mandatory requirement in Seattle since 2009, is also credited with helping to save lives.

“This could potentially have been much worse,” said Seattle Fire Department spokesman Kyle Moore. “You have an establishment full of patrons and an intentionally set fire. That’s a very dangerous situation.”

As of Thursday no arrests have been made and police say the motive for the fire was not clear.

“If there’s any indication it’s a hate crime, we’ll pass it on to our bias unit,” said police spokeswoman Renee Witt.

The incident occurred as Seattle’s first openly gay mayor, Ed Murray, took office.

Mr Murray, who spent his first morning touring the city’s emergency operations centre, said he was thankful no one was injured, but concerned that the club had been targeted.

“Right now, the most important thing is to find the individual or individuals responsible, and then determine the motive for this potentially very destructive action”.