GREENVILLE – Despite attempts by onlookers to rescue her, a seasonal resident of this scenic Piscataquis County town apparently drowned Thursday morning after her pickup truck careened down a hill and plunged into Moosehead Lake.

The accident that claimed the life of Linda Brown, whose age was not immediately available, was witnessed by about a dozen people who were near the municipal pier, close to the dock site for the steamship Katahdin, according to Police Chief Duane Alexander.

Brown was a summer resident of the town of 2,000 inhabitants, the police chief said.

Brown is believed to have drowned after the Chevrolet pickup truck she was driving traveled down the Pleasant Street hill from a residential area, crashed through a barricade and drove off the end of the pier near the heart of the business district, Alexander said.

Bystanders reportedly attempted to rescue Brown, who was trapped in her submerged vehicle, but their efforts were in vain.

Brown’s vehicle came to rest in an estimated 15 feet of water, Alexander said.

“We think it’s a mechanical problem,” Alexander said. He said the pickup was removed from the lake about 5 p.m. Thursday and that a state-certified mechanic would examine it today in an attempt to determine what went wrong.

An autopsy is scheduled to be performed on Brown today, the police chief said.

Although it could not immediately be confirmed, Brown apparently also resided in Jacksonville, Fla. Her name and town of residence appear in an online guest book on the “Exiles of Maine” Web site.