A second major Boston bank has disclosed that it failed to report about $191.2 million in large cash transactions with foreign banks over the past five years in violation of federal law.

The disclosure by Shawmut Bank of Boston, the city's third-largest, comes amid a major federal crackdown on domestic banks that are not complying with requirements that they disclose cash transactions in excess of $10,000.

The Shawmut disclosure -- made on the heels of the Bank of Boston's guilty plea to a felony charge of failing to report similar foreign transactions totaling $1.2 billion -- immediately spurred the interest of federal regulators, the U.S. attorney's office and a Senate subcommittee.

Federal officials have said repeatedly in recent weeks that the failure to report overseas cash transfers has helped drug traffickers and others involved in organized crime launder hundreds of millions of dollars in illicit profits through U.S. banks.

A Treasury Department official said yesterday the department was "pleased that Shawmut has come forward," and added there was no evidence at this point to indicate whether it was being used for the laundering of drug money or other criminal purposes.

But in keeping with its insistence that all reporting violations are a serious matter, the Treasury has referred the Shawmut case for "possible criminal investigation" to the Internal Revenue Service, a spokesman said.

The Shawmut violations, which a bank spokesman attributed to administrative oversight, were uncovered by an internal bank investigation that was initiated last month after widespread publicity over the Bank of Boston's problems, according to bank spokesman John Gould.

The bank found that since 1980, it has engaged in 1,800 separate transactions with seven foreign banks -- including banks in Spain, Portugal, Ireland and Canada -- that should have been reported to the Office of the Comptroller of the Currency, but weren't. In addition, the bank failed to report one 1983 transaction in which it shipped $5 million in cash to a Swiss bank that was a longtime customer.

The bank said in an official statement that the seven foreign banks had been erroneously placed on an "exempt" list along with 20 domestic customers, including nine educational, religious and health organizations and airlines, and 11 commerical firms located in Eastern Massachusetts.

Asked yesterday why the bank failed to report the transactions, Gould replied, "We missed it. It's that simple."

Although the federal law requiring disclosure dates to 1972, foreign banks and many domestic businesses were eligible for exemption until 1980, when the Treasury Department issued new and tighter regulations. Gould said that, when the regulations were promulgated, they were distributed to Shawmut's branch office, but not its separate currency department, which deals with foreign banks and large local customers.

In essence, the currency department was unaware of the reporting requirement for foreign transcations, until the bank began its internal investigation last month, Gould said. "On the 19th of February, we had in hand facts that day that made it clear we had a problem," he said.

The next day, bank officials informed the Treasury and the Office of Comptroller of the Currency. In addition, the bank retained a former U.S. attorney, John Martin, who yesterday met with U.S. attorney William Weld and submitted detailed information about the reporting failures.

Weld, who has previously said he is investigating other area banks beside the Bank of Boston, said yesterday that he was "reviewing the material that the Shawmut attorney gave us."

The Senate permanent subcommittee on investigations, which had scheduled a hearing next Tuesday on the Bank of Boston case, now has called Shawmut officials to testify, a spokesman said.