Low Water Pressure Hurt Effort in Apartment Blaze : Fire: Bursting pipes--not disconnected hydrants--are blamed. Damage in Thousand Oaks complex rises to $12 million.

THOUSAND OAKS — Fire officials investigating a Saturday blaze that destroyed 21 apartment buildings under construction in Thousand Oaks raised the damage estimate to $12 million Sunday and said firefighters were hindered by low water pressure in the nine hydrants serving the complex.

The investigators said they had no evidence that any of the hydrants were disconnected, as officials had said during the blaze Saturday. Instead, they said some hydrants were rendered useless as bursting pipes in the burning buildings caused water pressure to drop dramatically.

All units being built at The Knolls complex on Avenida de los Arboles had water connections, said Ventura County Fire Investigator Bill Hager. As the buildings collapsed, broken water pipes sent about 1,000 gallons of water a minute flowing down the streets, he said.

Hager said the investigation is continuing, but he speculated that officials on Saturday “jumped to a conclusion” that someone had disconnected the hydrants.

All the hydrants had been inspected by the Ventura County Fire Department before construction began to make sure they were operational, said John Wade, Fire Department spokesman.

Don Nelson, the city’s director of utilities, said that the water system provided twice as much water as required by fire codes but that the hydrant system is designed to fight individual fires, not groups of buildings burning simultaneously.

“It was an inferno,” Nelson said. He said city officials and the county Fire Department will meet to discuss whether changes are warranted.

Firefighters said they were beset by other problems during the fire that destroyed 330 of the 544 apartments at the complex. High winds, low humidity and the close proximity of buildings, coupled with the fact that the complex was in “the most volatile stage of construction,” contributed to the severity of the blaze, Wade said.

“It’s just a real dangerous, critical point of a construction job,” he said, noting that exposed wood building frames did not have the tile roofs that might have slowed the fire.

Some of the buildings were only 12 feet apart, Wade said. Wind gusts were clocked at 25 m.p.h.

On Sunday, gawkers climbed a nearby hill to gaze at the piles of rubble and watch the efforts of 86 firefighters. Clouds of smoke continued to billow through the area as bulldozers ripped down ruined buildings in search of smoldering embers.

The blaze was ignited about 3 p.m. Saturday by a plumber using a torch to solder a pipe, fire officials said. It destroyed 21 buildings and damaged another for a loss of about $10 million, Wade said. Another $2 million in construction equipment was destroyed. Wade said the loss is covered by insurance. The first damage estimates were placed at $7 million.

“There’s a lot of work the developers are going to have to do before they start back into rebuilding,” Wade said.

Officials of Newport Beach-based Regis Homes Corp., the project’s co-owner, declined to comment Sunday.

Officials at the Ventura headquarters of Interstate Plumbing Inc., which employed the plumber who accidentally started the fire, and at the Thousand Oaks offices of Lang Ranch Co., the project’s co-owner and developer, could not be reached.

About 250 firefighters from throughout the area fought the blaze at its height. Units came from Ventura County, the city of Los Angeles, Los Angeles County, Oxnard, Camarillo State Hospital, Point Mugu and state forestry and fire facilities.

Four firefighters suffered minor injuries.

“With the magnitude of destruction, we were fortunate to have only four injuries,” Wade said.

The fire was contained by 9 p.m. Saturday, but buildings continued to smolder through the night.

Times staff writers Aaron Curtiss and Philipp Gollner and correspondent Stephanie Stassel contributed to this article.