U.S. Ambassador Malcolm Toon said today it will cost about $5 million to repair the damage caused by last week's fire at the embassy here.

He said that much of the materials and new equipment to replace the demolished roof, gutted eighth floor and other floors damaged in the 18-hour blaze must be shipped in from the United States adding as much as 50 per cent to the costs.

Toon also acknowledged that there had been "a degree of looting" by Soviet firemen in the offices on the smoke-filled or burning upper floors. Reports have circulated here in recent days that some small items had been missed by embassy employees inspecting their offices and that the disappearances could not be explained by the fire or smoke.

The ambassador listed the items known to be missing as several small address books, several stamps for franking mail and for making security classifications on documents, a video cassette removed from the set of 12 cassettes of the television series "Roots" that had been lent to the embassy by ABC correspondent Lynn Jones, and a small sterling silver medallion.

Despite these incidents, Toon reiterated that he is certain that the security of top-secret materials and qequipment in the embassy was not breached.

"We've made a pretty complete check and I am satisfied that nothing of consequence is missing," he said. He also reiterated that he believes that Soviet firemen conducted themselves generally well during the fire. Sensitive documents are normally marked in such a way that it can be readily ascertained whether some item is missing, and that is apparently what Toon was referring to.

The address books were missing from the desk of press counselor Raymond Benson. He said they contained addresses of friends and acquaintances from countries other than the Soviet Union. The franking and security stamps were missing from various desks in offices on the eighth floor press and cultural section.

The set of 12 "Roots" cassettes were on a couch in the cultural section Friday afternoon before the fire broke out. Later, American employees found 11 cassettes; episode No. 6 was missing. The medallion was taken from the wall in Toon's ninth floor office. He said it had been there when he arrived as ambassador and he was not sure what it commemorated.

Toon made these additional disclousures: two embassy staffers have requested permanent transfer from here because of the strain of living here: he supports a request by a State Department employees' group for a raise in the hardship pay to 25 per cent from 20 per cent over base salary for the time - estimated at three to four months - needed to rebuild the embassy.

Such pay is normally granted only in "seriously dangerous areas, where people are likely to be shot at." Toon said. But he said the pay is justified during the rebuilding time.

He added that a cause for the fire "still has not been pinpointed" but said he and other officials are quite sure it was an electrical malfunction in an office on the eighth floor.