HAMPTON — The cause of a four-alarm fire which caused major loss to a seven-unit apartment building at 707 Ocean Boulevard on Saturday remained under investigation this week, but does not appear to be of a suspicious nature, according to Hampton Fire Inspector Jonathan True.

Rain was falling and the skies had darkened at 5:27 p.m. Saturday, the time the first alarm was sounded. True said the three-story, wood frame structure was fully involved when firefighters arrived on the scene. An off-duty firefighter had already started kicking in the doors, he said.

The building, which housed 11 tenants, is owned by Arthur Labrie. No injuries occurred as a result of the fire, which caused major damage to the second and third floors, and smoke damage to apartments on the first floor.

With billowing smoke often obscuring the view of the crowds of spectators assembled outside the yellow police tape cordoning off the area, more than 100 firefighters from 10 communities fought the blaze, making aggressive interior attacks and searches, True said. Their efforts were hampered by "rapidly deteriorating conditions," said True, as the winds shifted to the east due to an approaching storm. "The building itself became unsafe for firefighters," True said, making it necessary to order them to evacuate the building.

True said the building was not fire-resistant, and was quite dry. The structural members (posts and beams) had failed, according to True. Decks on the rear of the building had totally burned right through, he added, and there was partial collapse of the roof. Minor damage occurred to the building five feet south of the fire, while no damage was reported to the residence standing 15 feet north of the fire.

True said the three or four ladder pipes used were pumping 3000-4000 gallons of water a minute, in addition to hand lines being used. He estimated water output to have been at 6000- 7000 gallons a minute. "The water system didn't fail; we overtaxed it," True said.

Less than two hours after the fire began, flames were still shooting through the ocean side of the building, as skies cleared overhead. Firefighters from as far south as Newburyport, Salisbury, and Amesbury, Massachusetts, joined in the effort to extinguish the stubborn blaze, as well as firefighters from Seabrook, North Hampton, Rye, Portsmouth, Stratham, and Exeter. The time of the "All Out" was 7:10 a.m. on Sunday morning.

The building did have smoke detectors and did have a certificate of occupancy, True said, and has been released to the owner. True said he expects his department to have completed its investigation by Friday. As of this paper's deadline on Tuesday, two pets, a cat and a dog, had not been located. True said he remained optimistic that the chance exists that both escaped when the doors were first removed.