Firefighters are working to extinguish a blaze that broke out on the historic Oceanside Pier in San Diego.

The fire was reported around 3 p.m. PT inside the vacant building that previously housed Ruby's Diner on the pier.

Local fire crews were joined by Cal Fire and the San Diego Sheriff's Department to make a water drop on the structure fire, reported NBC San Diego.

Two fire-fighting vessels are working to battle the blaze that has charred the building and caused the roof to collapse.

'What we know is that the fire teams decided to do a defense tactic and not try to save the restaurant but save the rest of the pier.' Oceanside mayor Esther Sanchez told the local news station.

'The Oceanside Fire Department is currently engaged in fighting a fire on the Oceanside Pier. We are asking all citizens to please stay away from the immediate area,' the fire department said.

Photos and video show plume of smokes rising from the wooden structure as crews work to put on the flames.

'Restaurants at the end of the Pier are damaged, as is the end of the Pier structure,' the City of Oceanside said.

'No injuries have been reported. Personnel from The Brine Shop and the Bair Shop are all accounted for.'