ARUNDEL – A boatyard fire that caused an estimated $150,000 in damage appears to have been set intentionally, investigators said.

The state Fire Marshal’s Office and local police are investigating Sunday morning’s fire at the Southern Maine Marine Center.

The fire shut down U.S. Route 1 for nearly four hours, raising concerns of Secret Service agents who wanted to make sure President Bush could still get through in case of an emergency. Bush was on vacation at nearby Walker’s Point in Kennebunkport.

Explosions were reported as firefighters made their way to the scene. A large metal workshop at the boatyard was filled with flames when firefighters arrived. Because there is no fire hydrant near the building, it took firefighters nearly a half-hour to get water to the site. Magnesium boat parts in one of the buildings could not be extinguished with water, so foam had to be used instead.

Five boats, a storage shed and a warehouse were lost, but a trailer used to store oil was saved.