PORTLAND — A Portland fire captain and firefighter are suspended without pay after a preventable accident Saturday during which a fireboat struck an obstacle in Casco Bay.

Twelve civilians, including family members, were onboard the boat when the accident occurred about 6 p.m., according to a press release from Nicole Clegg, spokeswoman for the city.

The impact of the collision, just north of Fort Gorges, caused damage to a propeller shaft, propeller and rudder. The accident caused an estimated $38,000 in damage.

The accident resulted in an investigation by Fire Chief Fred LaMontagne, which led to the suspension of Firefighter Joseph Murphy and Capt. Christoper Goodall who “failed to comply with common practices and U.S. Coast Guard navigation rules to ensure the safe operation of the vessel,” the release said.

According the the release, Goodall allowed civilians to accompany the crew on a training exercise. Civilians are allowed on the boat under certain circumstances. Because of the incident, the fire department is reviewing its practices and policies regarding transportation of civilians and will make changes as necessary.

It was the City of Portland IV’s second accident since it was put into service in September 2009. The $3.2 million boat ran aground in November 2009 in Whitehead Passage, the channel between Peaks and Cushing islands, causing $90,000 in damages, which took three months to repair.