Canadian authorities yesterday brought 28 new charges against three residents of Montreal in connection with a series of shipments to Pakistan of U.S.-made electronic equipment that allegedly could be used in the manufacture of nuclear weapons.

The three Canadians, one an engineer who emigrated to Canada from Pakistan, face 11 charges of exporting tomic-energy material or equipment without a permit, a violation of the Canadian Trade and Commerce Act.

A spokesman for the Royal Canadian Mounted Police (RCMP) said these charges stem from 11 alleged shipments made since last April to Pakistan of U.S.-made parts for an inverter, a sophisticated device needed for a uranium-enrichment plant in Pakistan that could produce weapons-grade uranium. The value of the shipment was estimated at $144,000.

The three men also face 14 charges of exporting goods originating in the United States without a permit and three charges of exporting microcircuits without a license. Each violation carries a maximum penalty of $21,000 and five years in prison.

The charges filed yesterday replace a single charge of exporting U.S. goods without a permit, which was brought against the three men last week. This was a preliminary step while other charges were drawn up, according to government officials.

A year-long investigation by the RCMP led to the seizure of $42,500 worth of electronic equipment Aug. 29 as it was about to be flown out of the country. An RCMP spokesman said today that, according to records obtained by police, 10 other shipments got through prior to Aug. 29. He said he did not know when the RCMP became aware of the shipments.

Amid persistent reports that Pakistan is trying to develop a nuclear weapon, Britain, the United States and other countries have taken steps to block the export of strategic equipment that Pakistani scientists might need to build such a bomb.

Pakistan has consistently denied that it is attempting to manufacture nuclear weapons.

Charged were Salam Elmenyawi, 31, Mohammed Ahmad, 44 and Abdul Aziz Khan, 40. Elmenyawi is a businessman from Egypt, Ahmad is a mechanical specialist from India, and Khan is an engineer originally from Pakistan. The three, all Canadian citizens, will appear in court Jan. 15.