A unique pre-Revolutionary war house on the planned site of a new shopping center in Olney was largely destroyed by fire early last Sunday morning. Montgomery County fire officials said they are investigating the possibility of arson in the blaze.

Fair Hill Farm, for many years the home of Washington-area developer Don R. Lamborne, who threw elaborate parties there in support of civic activities, was burned out by the unexplained fire at 12:15 a.m. Sunday. Fire officials said there was $200,000 in damage.

A barn on the same 28-acre estate was destroyed by fire at 5:15 p.m. on Tuesday. Fire investigator Carvel Harding said the barn was definitely set on fire.

Harding said the house fire is viewed as "a suspicious fire" because "we have elminated all accidental and natural causes." He said he has additional evidence pointing to arson in the case of the house, but could not disclose it. "We're still working on it," he said.

Lamborne and his wife recently lost ownership of the house after a series of financial transactions led to a court battle and a takeover of the property by a partnership controlled by parking lot executive Dominic F. Antoncilli Jr., according to Montgomery County court officials and other legal sources.

Antonelli's partnership, Olney Shoppers' World Associates, plans to build the shopping center on 18 acres of the farm, according to the officials and sources.

While the house is in the path of the proposed shopping center, the officials and sources said that an agreement between Lamborne and Antonelli would have allowed Lamborne to have the house moved out of harm's way had he remained in possession of it.

Antonelli is currently under investigation by federal prosecutors probing a possible connection between a $33,000 loan to former D.C. human, resources director Joseph P. Yeldell and a department lease of an Antonelli-owned building.

According to official records and legal sources, Antonelli lent $650,000 to the Lambornes on May 30, 1973, a loan secured by the deed to Fair Hill Farm.

At the same time, souces said, Antonelli obtained from the Lambornes an option to lease the 18-acre portion of the land for a shopping center.

But Antonelli was unable to obtain sewer permits for his shopping center for a long time and never exercised that option, sources said. They said that the lease payments would have covered the Lambornes' loan repayments to Antonelli.

But court records show that the Lambornes, who could not be reached for comment, defaulted on those repayments and on Sept. 3, 1975, the property was sold in a foreclosure auction for $500,000 to Antonelli.

The Lambornes fought this is in court, but their objects were overruled and the sale was ratified by Montgomery County Circuit Judge Joseph M. Mathias on Jan. 3, 1977. The Lambornes' appeal of this decision is pending.

Shortly thereafter, Antonelli assigned his rights to the property to Olney Shoppers' World, according to court records.

The Lambornes continued living in the house, the records show, and on April 13, 1977, attorneys for Olney Shoppers' World obtained a court order directing the Montgomery sheriff to evict them. The Lambornes appealed this court decision and that appeal is also pending.

Circuit Judge John F. McAuliffe last Friday gave the Lambornes until 9:30 a.m. on Tuesday to either move out or put up a $250,000 bond that would compensate Olney Shoppers' World for any losses incurred while the Lambornes remained in the house pending the outcome of their appeals. The bond was not posted.

County fire officials said the house was vacant at the time it burned on Sunday.