Losses at the nation's savings and loans more than doubled in the last quarter to $631 million, mainly as a result of collapsing real estate values, the federal Office of Thrift Supervision reported yesterday.

Even with the transfer of 64 of the weakest thrifts to government control in the June-September quarter, the OTS said the remaining 2,389 institutions averaged heavy losses because they had to set aside $2.16 billion to cover loans expected to go bad.

Losses in the first and second quarter of the year combined were $675 million.

OTS Director Timothy Ryan said the thrift losses were due to a commercial and residential real estate slump that has affected much of the United States. Fourth-quarter losses, he said, are likely to be even worse.

Ryan noted that commercial vacancy rates are up nationwide and housing starts are at their lowest level since 1982.

"As long as the real estate slump continues, the thrift industry will have a tough time improving performance," said Ryan.

The OTS, which regulates the nation's savings and loan institutions and is responsible for the cleanup of failed thrifts, noted that Virginia thrifts have among the nation's highest percentage of overdue real estate loans: 5.30 percent.

Of Virginia's 56 thrifts still in private hands, the OTS has classified 17 as troubled or likely candidates for government takeover. Losses for Virginia thrifts were $70 million.

The OTS figures reflect the abrupt end during the last year of of Northern Virginia's building boom.

"An awful lot of people just can't make their payments," said William Lauer, vice president of the Northern Virginia Building Industry Association. At the same time, there are few people buying real estate right now -- new home sales in the region are down 47 percent, according to one recent survey.

"There is simply no place for developers to get the cash to make the payments," Lauer said. "Interest meters on a project run no matter what."

The OTS reported that only two states had more overdue real estate loans than Virginia: Rhode Island, with 9.5 percent, and Massachusetts, with 6.91 percent.

District thrifts had relatively few overdue real estate loans, 1.48 percent, and Maryland thrifts had 2.13 percent. One of the District's four thrifts and 13 of 93 in Maryland are classified as troubled or imminent candidates for government takeover. The agency declined to identify the institutions.

Thrift losses and failures have spread from the Sun Belt states to the Eastern Seaboard, and now to the Far West, where some of the nation's largest thrifts are located.

Western thrifts, which have more than one-third of the industry's total assets, lost $203 million.

The Resolution Trust Corp., the federal agency that is disposing of failed thrifts and paying off depositors, will report next week on the losses incurred last quarter by 206 thrifts operating under conservatorship.

The OTS classifies thrifts in four groupings: Group 1 thrifts, which numbered 1,130 in the third quarter, are considered well-capitalized and profitable; the 685 thrifts in Group 2 meet or are expected to meet capital requirements; the 356 thrifts in Group 3 are troubled, with poor earnings and low capital; and 218 thrifts in Group 4 are expected to be taken over by the RTC.

The consolidated net worth of the assets held by Group 4 is a negative $3.7 billion, according to the OTS. Ryan told a congressional panel this week that 80 of those thrifts are essentially insolvent now and will by taken over by the RTC as soon as scheduling permits.