WASHINGTON, June 24— The State Department said to day that a third Pakistani freighter loaded with military equipment sailed from New York for Karachi after the United States had banned de liveries of arms to Pakistan.

Department officials said the vessel, the Kaukahia, left New York on April 2, a week after the Pakistani Army moved to crush the autonomy movement in East Pakistan.

The officials said they had “reasons to believe” that the freighter carried equipment for the Pakistani armed forces that was purchased under the United States foreign military‐sales program and from commercial suppliers.

The other Pakistani ships known to have sailed with a military cargo after the ban on new deliveries were the Sunderbans, which was due in Karachi yesterday, and the Padma, which sailed from New York last Tuesday.

The State Department reportedly discovered only yesterday that a third vessel was involved in the controversial shipments. But it was not able to identify the Kaukahia until late today. She reportedly arrived in Karachi late in May.

In the wake of these developments, Secretary of State William P. Rogers today ordered the creation of a special study group of senior officials to determine how the Administration's policy banning deliveries of arms to Pakistan was being implemented.

In a separate action, the United States announced it was providing an additional $70‐ million to India to help care for the estimated six million East Pakistani refugees now on Indian territory and to shore up the Indian economy.

The announcement coincided with Indian protests against the reported shipments of United States military equipment to Pakistan.

Mr. Rogers ordered the inquiry as differing statements were made about the circumstances under which one of the ships — the Padma — had been boarded and searched by United States customs agents to determine her cargo.

Lieut. Gen. Robert H. Warren, who is Deputy Assistant Secretary of Defense for Military Assistance and Sales, testified this afternoon before the Senate Appropriations subcommittee on foreign operations that “we had the ship stopped at sea and United States customs officials went aboard to examine her cargo.”

But a Defense Department spokesman said later that General Warren's remarks were misunderstood and that the boarding actually took place in the Port of New York before the Padma had sailed for Montreal.

Customs Bureau officials here were unable to provide a full account of the checking of the Padma cargo. But one official said his understanding was that customs agents in New York had simply compared the ship's manifest with State Department licenses authorizing the exports before the Padma sailed.

The Padma, whose interception was requested today by the Indian Government, was re ported late today to be in the St. Lawrence Seaway bound for Montreal.

General Warren told the sub committee that the customs agents “found no aircraft” aboard the Padma. The New York Times reported Tuesday that the Padma's bills of lading had shown the loading of eight items marked as “aircraft.”

But informed sources said to day that the equipment described as aircraft were small, radio‐ controlled pilotless “drones” designed to serve as practice targets for antiaircraft gunners.

General Warren described “at least three‐fourths of the ship” as carrying auto parts” and “spare parts” purchased by Pakistan under the military sales program or commercially, before March 25, when the army crackdown began in East Pakistan. Official sources here said that these parts were for military vehicles and aircraft.

Copies of State Department export licenses for a number of items shipped last month aboard the Sunderbans showed that they covered military‐use items.

A State Department spokesman, Charles W. Bray 3d, said that while the Administration order to halt issuing licenses for military sales to Pakistan was meant to have been effective on March 25, it did not actually go into effect until April 6.