Several dozen Ugandans are in the United States for training with private organizations, the U.S. embassy in Nairobi, Kenya, said yesterday. The disclosure adds to the burgeoning issue of whether the United States has unwittingly been providing assistance for Idi Amin's government.

The State Department confirmed Monday that a dozen Ugandans were in a private training course for helicopter pilots run by Bell Helicopter Co. in Fort Worth, Tex., but department spokesmen yesterday were unable to add to a report from the embassy in Nairobi that as many as 40-to-50 Ugandans are in the United States for other private run training programs.

The State Department said Monday that it is "tightening up" on visa procedures for Ugandans since their travel to the United States is "possibly incompatible" with Uganda's record on human rights.

Rep. Michael T. Blouin (D-Iowa) charged yesterday that the helicopter pilots are "Adi Amin's agents of torture and oppression." He sent a letter to President Carter calling on him to revoke the visas for the Ugandan pilots.

Blouin's office said that more congressmen are expected to join in the appeal.

The White House press office had no comment yesterday on the visas for the Ugandans, but a White House source said that he "wouldn't be surprised" if the President's staff took up the issue.

There was some confusion over just what kind of visa the Ugandan helicopter pilots were issued.

The White House said it was under the impression that tourist visas were involved and one source said, "We're trying to figure out whether we've been had."

The State Department press office said yesterday afternoon, however, that the visas were for government employees traveling for official purposes.

The department spokesman said that visas of this sort did not have to be cleared in Washington under the procedures in effect at the time. They were issued in late September.The embassy spokesman in Nairobi said:

"There is really nothing unusual about this. Because we do not have an embassy in Kampala we routinely handle official requests from the Ugandan government for visas in Nairobi."

The United States closed its embassy in Kampala, the Ugandan capital, in November 1973, but did not break diplomatic relations.

The State Department had no explanation yesterday as to why the question of human rights considerations had not entered into visa applications by Ugandans before the issue of the helicopter pilots' presence emerged in the press.

A department spokesman said, however, that "we have instructed our posts to refer to Washington for review all future applications for all Ugandan officials and employees."

The spokesman added that the department is reviewing the question of whether the 12 Ugandan pilots can be expelled under a provision that their presence could have "serious adverse effects on our foreign policy."

The State Department said it did not know how many Americans might be traveling or working in Uganda, aside from about 250 missionaries.