A federal grand jury here has expanded its investigaion of alleged irregularities in the awarding of Metro contracts to include a total of $100 million or more in contracts for Farecard machines, elevators and escalators, according to sources familiar with the investigation.

The investigation has become so large that FBI agents and federal prosecutors have gone to Metro headquarters several times recently to study cartons of documents subpoenaed by the grand jury, Metro sources said.

In addition, many persons familiar with the internal details of how the contracts were awarded have been questioned by investigators as part of the expanded inquiry, sources said.

The investigation is the first major inquiry into the lucrative contracts awarded for Washington's growing Metro system, which will cost about $7 billion to complete over two decades. Described in the past as the world's largest public works project Metro has already cost $2.3 billion through last week's opening of its newest stations in Arlington.

The $60 million elevator contract under investigation was won by U.S. Elevator, a subsidiary of Cubic Western, the company that won a $43 million Farecard contract away from another firm in 1974.

The elevator contract was won through sealed bid. The current investigation is believed to focus on how Metro handled various requests by U.S. Elevator for delays in implementing the contract after it was awarded.

The $5 million escalator contract under investigation was ultimately awarded to Westinghouse because of a motor design that the company developed to deal with varying lengths of escalators needed for Metro stations around the Washington area.

The investigation surfaced in October when prosecutors said they had reopened a criminal investigation into allegations that a midlevel Metro contract administrator, Edward Jasnow, had received $38,000 from a Washington consulting firm hired by Cubic Western.

Jasnow had denied any wrongdoing in connection with the receipt of the money.He was fired two weeks ago by Metro for his failure, under internal conflict-of-interest regulations, to report he had received the payments.

Assistant U.S. Attorney Jeffrey T. Demerath of the fraud division declined to comment about the investigation.

Metro officials would say only that Jasnow has been fired and that their understanding is that the grand jury is investigating several contracts. Metro investigators have said in court documents that the agency is conducting internal investigations into possible improper conduct in the handling of contracts by several employes.

Jasnow's attorney, Michael G. Scheininger, said Jasnow was informed that he was being fired for a "technical" conflict-of-interst-of for failing to report the $38,000 in checks he received from E.C.M. Associates, a consulting firm hired by Cubic Western here for work on Metro contracts.

Jasnow has maintained that the money he received was for work with E.C.M. that was unrelated to his Metro Job.

According to previous statements he has made, Jasnow said he advised E.C.M. Associates in connection with contracts submitted to the Navy Department.

Jasnow's actions surfaced in a lawsuit involving Metro, Cubic Western, and the firm that originally had the Farecard contract, Control Data Corp.

Control Data has accused Cubic Western in the suit of using commercial bribery to steal the contract that was awarded. Metro also is involved in the suit in an attempt to recover money it said it lost in the contract-awarding process.

Metro said early last month that it believed some of its employes were given small gifts by Control Data in return for access to confidential internal Metro documents.