A group of leading American businessmen who had just completed a week of cordial and productive talks here with Vietnamese officials were searched and harassed for 2 1/2 hours at Hanoi's airport as they sought to leave the country.

The Businessmen were members of the American Chamber of Commerce in Hong Kong and had been invited to vietnam by its Chamber of Commerce. Letters and documents carried by the Americans were seized and some members of the 10-man group were pressured to sign statements that they had violated Vietnamese regulations.

The incident, which appeared premeditated, took place last Friday. It fueled speculation that Vietnam's leadership is divided about improving relations with the United States.

Nguyen Co Thach, Vietnam's minister of state for foreign affairs and senior Vietnamese negotiator on normalization of U.S. Vietnam relations, was among passengers kept waiting in sweltering heat as the Americans were singled out for investigation by airport security officials.

Thach later personally apologized, saying the incident was not "policy." He ascribed it to those who are "too zealous" in their work.

"After 30 years of war, our people have too much doubt about foreigners," he said. "Such things are not in your interest and they are not in our interest. It is not my responsibility, but I am sorry."

Thach said that he would have intervened had he been informed. Noi Bay airport consists only of a few small buildings. The American Group asked their interpreters and escorts to contact the Foreign Ministry and Thach in particular. They were told both that the Foreign Ministry could bot be contacted and that Thach was unlikely to get involved.

"They are the security people. No one can do anything," said one embarrassed Vietnamese escort.

Later, as the group was finally boarding the plane, the same escort advised one member of the group that Thach would be abroad the plane and that the group should try to contact him.The Chinese and Italian ambassodors to Hanoi were among passengers kept waiting as the flight's departure was delayed.

Robert Adams, president of the American Chamber of Commerce in Hong Kong and leader of the group, refused to sign a statement and finally was allowed to board the flight. Some other members of the group signed only after adding denials that they had violated any law and they were signing under duress.

Adams, who is vice-president of the American Chamber of Commerce in Hong Kong, also refused to turn over photocopied chapters of books and articles on Vietnam and was finally allowed to leave with them. Aboard the plane. Thach later told adams he was right not to sign.

Vietnamese security officials also took copies of an organization chart of the Vietnamese government prepared by the National Foreign Assessment Center of the Central Intelligence Agency, and U.S. government transportation maps of Vietnam. Both are freely available from U.S. diplomatic missions. They had been used openly in the course of the delegation's discussion with the Vietnamese.

Thach took a list of all items seized and promised that they would be returned. He described the seizures as "foolishenss."

Among other items taken by Vietnamese authorities were between 150 and 200 letters being carried by Richard J. Bullis, executive director of the American Chamber of Commerce in Hong Kong. Residents in Ho Chi minh city (Saigon) had given Bullis the letters. Most were directed to relatives abroad or to the U.N. High Commission on Refuggees in hope of locating missing relatives.

In addition to Thach, the American delegation had met Minister of Petroleum Dinh Duc Thien and senior officials form petrovietnam, the state oil and gas development company. Discussions had been frank and cordial, and the delegation had been taken to Petrovitenam's offshore exploration base at the southern coastal city of Vung Tau.

All members of the delegation were searched with exception of John F. Goudey, director of business research for Union Carbide Eastern Inc. of Hong Kong. Goudey is a Canadian. All others in the group were American. No other passengers on the Vietnam Airways flight from Hanoi to Bangkok were more than cursorily checked before boarding the flight.

Security officials wanted to search me behind closed doors, but did not press the point when I refused.

Escorts provided by the Chamber of Commerce said they were powerless to intervene. Bung Tri, a former Vietnamese Army captain now with the Chamber of Commerce, penned the following message as the group left:

"Anyone who comes to Vietnam as friends will be received with respect and friendship . . . We are looking forward to cooperation with American businessman and companies in the principle of mutual respect and mutal benefits."