A predawn blaze that apparently originated in an unoccupied houseboat quickly spread to four other vessels moored at the Columbia Marina at the Pentagon Lagoon early yesterday, causing about $25,000 in damages, officials said.

D.C. fire investigators said two of the boats, which ranged in length from 22 to 33 feet, were completely destroyed.

The marina manager Michael Walwer, said that the fire started at about 4:48 a.m. and the heat from the flames was so intense that the fire spread to the other boats, "even though there was no wind at all last night."

It was the third fire since mid-May at the fashionable 532-slip marina, located just off the George Washington Parkway, and some boaters there yesterday were expressing concern over the number of accidents there.

During a harsh May thunderstorm, an electrical fire from a lamp caused extensive damage to a 21-foot fiberglass cruiser. Another fire in June burned the interior of a second craft after a television set apparently overturned, Walwer said.

"I can understand (the boaters') concern, but all of these accidents have been accidental," Walwer said yesterday.

"The boat owners should realize that as little electricity as possible should be left on boats that are unoccupied," Walwer said.

Witnesses told authorities that they heard an initial explosion, and that the fire raged through the boats "like they were made of dry paper," D.C. firefighters had the fire under control within 20 minutes of arriving on the scene.

Sgt. Ron Wilkins of the District's Harbor Patrol said "all indications point to an accidental cause to the fire." A fire inspector added that a short circuit in the houseboat had probably started the blaze.