ROCKLAND (AP) – State fire marshals are investiating whether a recent restaurant fire has connections to a string of blazes this year in Rockland.

State fire officials will work with the Rockland Police Department in a joint investigation, state fire marshal Sgt. Joel Davis said.

Most recently, a waterfront fire last week destroyed a popular restaurant known as The Black Pearl. The building sat on a long pier jutting into Rockland Harbor and had recently reopened as Grapes Restaurant.

Senior Fire Investigator Tim York of the fire marshal’s office said on Tuesday the fire was caused by arson. He declined to specify what exactly was used to start the fire because that information is part of the investigation.

The fire started at an end of the pier that extends underneath and enclosed walkway. Firefighters battled the early morning blaze for about an hour but were at the scene for many hours cleaning up. At one point, the Fire Department contacted the U.S. Coast Guard to see whether it could provide assistance.

There are no suspects at this time, he said.

Petty Officer Jeremy Gourde said there are limits to what the Coast Guard can provide to local agencies. The only boat the Coast Guard could have used to responded to the fire, which took about an hour to extinquish, was a patrol boat.

But low tide would have made it difficult for to maneuver the vessel in that area, Gourde said. The weather also was too rough for the Coast Guard’s 25-foot rigid-hull inflatable boat, which already is winterized on land.

The pier, which was leased last summer by Maine Boats & Harbors, does not appear to be significantly damaged by the fire, officials said.