WASHINGTON (AP) _ The Justice Department has cleared its top anti-pornography prosecutor of allegations that he ordered the destruction of a sensitive document and that he traveled at taxpayer expense to religious meetings.

In a two-sentence letter, Michael Shaheen, head of the Office of Professional Responsibility, said that a criminal investigation of H. Robert Showers has been concluded and that the allegations ''were not substantiated and this office considers the matter closed.''

OPR is the unit that examines accusations of improper conduct or criminal activity by Justice Department employees.

The letter, sent to Showers' attorney, Stephen H. Galebach, did not specify the allegations.

But government sources have said Showers came under scrutiny earlier this year after he allegedly asked a colleague to destroy a memo in connection with a pornography case.

In addition, said the sources, speaking on condition of anonymity, investigators tried to determine whether Showers scheduled official trips at taxpayer expense that permitted him to attend meetings of Christian religious groups in his hometown of Raleigh, N.C., and other cities.

Showers in 1986 was chosen to head the Justice Department's National Obscenity Enforcement Unit by then-Attorney General Edwin Meese III.

He had been an assistant U.S. attorney in Raleigh before coming to Washington as a special assistant to Meese.

Showers, a deputy assistant attorney general, had been placed on administrative leave.