The FBI and federal bank examiners are investigating allegations that several questionable loans may have been made by Jefferson Bank and Trust Co., one of Prince George's County's most politically well-connected banks.

The investigation was sparked by questions raised by bank officials over one $25,000 loan authorized by Thomas C. Pulliam Jr., the bank's executive vice president. Jefferson's board of directors recently filed suit charging Pulliam with authorizing an improper loan to an "accomplice" who used an alias "for the purpose of defrauding the bank."

Bank officials said they have told investigators that $10,000 of the loan may have been used improperly. The FBI and bank examiners are looking at Pulliam's role in the loan in an effort to determine where the $10,000 went.

Pulliam, who was placed on leave by the bank, could not be reached for comment this week.

FBI officials would say only that the bureau is investigating allegations that at least one officer of the bank may have violated bank fraud and embezzlement laws. According to several bank officials, the FBI as well as the FDIC are looking into the $25,000 loan as well as other transactions involving Pulliam.

Jefferson board chairman Charles A. Dukes Jr. said that Pulliam was one of four people at the bank who were able to authorize substantial loans without having to get prior approval from the bank's board of directors.

Jefferson, located in Capitol Heights, is a small, independent bank that was formed in January 1979 by some of Prince George's County's most prominent businessmen and politicians. In addition to Dukes, a Republican fund-raiser and a member of the county planning board, the bank's board of directors and stockholders include Prince George's County Executive Lawrence J. Hogan and his wife, Ilona; banker and liquor board member Gerard Holcomb, and Raymond LaPlaca, a businessman active in Republican politics in the suburban county.

Jefferson's board of directors hired Pulliam as executive vice president in May 1979 from the Bank of Bethesda, bank officials said. For the last year he has been Jefferson's chief operating officer under Dukes, who has been serving as president and board chairman.

During the past year Pulliam has supervised or authorized hundreds of loans and bank transactions, Dukes said. The one transaction now being investigated was a $25,000 loan authorized by Pulliam to a man known on bank records as Robert Baker, according to the suit filed by Jefferson in Prince George's County Circuit Court.

According to sources, after the $25,000 loan was issued the person identified in bank records as Robert Baker took the money to a Virginia bank and had it converted into two cashier's checks, one for $15,000 and one for $10,000. The FBI is now attempting to determine who received the $10,000 check.

In its suit the bank alleges that Baker is an alias for an accomplice of Pulliam's and that Pulliam knew that and "intentionally and deliberately authorized the bank to release funds" in order to defraud the bank.

Dukes said this week that bank officials were scrutinizing several other "questionable" loans but they believe that no more than a total of $25,000 to $30,000 of the bank funds were involved.

"It's an embarrassment, it's unfortunate and its going to cause some loss to the bank," one official said. "But it was caught quickly enough that it won't make that much difference."

Dukes said that the bank, which concentrates on commercial loans, has grown from $2 million in assets when it opened in July 1980 to its current assets of around $14.5 million. Total deposits are now around $10 million.