The booking records include the men’s passport numbers, with six of the seven having the prefix “20”. That denotes a passport used for official state business, issued to government officials on foreign work trips and military personnel stationed abroad, according to an edict published by the Russian government and a document on the Russian foreign ministry’s website.

Reuters was unable to determine what the seven were doing in Iran.

A senior Iranian defence ministry official said Russian missile experts had made multiple visits to Iranian missile production sites last year, including two underground facilities, with some of the visits taking place in September. The official, who requested anonymity to discuss security matters, didn’t identify the sites.