A predawn blaze destroyed two barns, a year's supply of feed, and nearly $200,000 of equipment Saturday at the H Ranch near Abbotts Lagoon in the Point Reyes National Seashore.

The cause remains undetermined, and the investigation was closed Wednesday, fire officials said, noting electrical problems or an appliance could have sparked the blaze. Total damages are estimated at $500,000.

The fire destroyed 60-year-old hay and milking barns used by the Grossi and Evans families since 1939. The Park Service bought the 1,148-acre dairy ranch from Alfred Grossi in 1971. The ranch and buildings were eligible for the Register of Historic Places.

"They are historic buildings, really irreplaceable," said Don Neubacher, National Seashore superintendent. "[The barns] were in a national park, and we're going to work with Alfred Grossi and the Evans so that the new building style fits into the landscape of the north [park] district."

Insurance coverage may replace the structures at a depreciated value, funding only smaller replacement buildings, he said. The buildings had totaled 6,000 square feet.

It was a tremendous loss for Grossi, his daughter Dolores, and her husband Dan Evans, who now lease the government-ranch site to raise beef cattle, Dolores Evans said.

Insurance coverage for the barns' contents was uncertain, she said. Even the immediate loss of feed may require some livestock to be sold or the family going into debt, she said.

The Evans had planned to expand their operations so their 24-year-old son David, who graduates from college in December with an agricultural business degree, could return to the family business, she said.

"It's going to ... turn us around for a couple of years, but we're not going to give up," Evans said.

About $25,000 of hay had been stored in the barn to feed 450-head of cattle through February, Evans said. It was reduced to ash or bulldozed and soaked. Along with the seven truckloads of hay, eight tons of oats and also silage stored nearby were scorched and destroyed.

Four trucks, three all-terrain vehicles, two boats, a bandsaw, generators, and various ranching tools together worth $200,000 were destroyed, Evans and fire officials said.

The buildings were priceless, she added. Grossi and his father had built and remodeled many of the homes and structures on the ranch. "My father was devastated," Evans said.

Dozens of neighbors and friends have called or come by to help, she noted. Some brought gifts such as a hammer or shovel. Others are still lending a truck and hired hands to haul away charred metal and debris. Calls with moral support are pouring in, she said. "You can't ask for better neighbors or better friends," Evans added.

Evans said she was awakened by her dog early Saturday morning and ran outside to find the barn already in flames. Sparks rained down into her hair and vehicle gas tanks exploded as the family rushed 60 young cattle out of the area, three of which were burned as they ran out of the collapsing barn.

Flames leapt from thousands of hay bales stacked 30-feet high, and blazed to the top of 100-year-old eucalyptus trees nearby, said Mike Meszaros, the Inverness fire chief. Flames could be seen from Inverness Ridge and the hills above Hearts Desire Beach.

Lack of wind and quick firefighter response dampened any chance for the fire to jump to other structures.

About 40 firefighters contained the blaze within an hour, said county fire engineer Joel Chandler. A Point Reyes Station engine was first at the scene 11 minutes after the 3:14 a.m. call, followed by engines from Inverness, Woodacre, Hicks Valley, the National Seashore, and water trucks from Ross and Novato, he said.

The fire followed a heat wave last week, noted Inverness Fire Chief Meszaros.

County fire investigator Chris Collins said there was not evidence of arson or spontaneous combustion.

Heat generated by decomposition can cause hay to spontaneously combust, but the hay burned in the H-ranch barn was chemically treated to prevent spontaneous combustion, Collins said.

Rancher Dan Evans had recently tested the moisture content of hay in the barn, finding it dry and posing no threat of spontaneous combustion, Superintendent Neubacher said.

In his book Ranching on the Point Reyes Peninsula, historian Dewey Livingston wrote that "about 1930, the large dairy barn built in 1883 burned at milking time, reportedly due to spontaneous combustion of green hay. ... Twenty-three cows died in the fire when milkers ran to save their houses."

The hay barn which burned Saturday had been built to replace the barn lost 66 years ago.