Updated

The British government has issued an alert to airlines around the world, urging them not to allow former U.S. intelligence contractor Edward Snowden to board flights to the United Kingdom.

The alert, dated Monday on a Home Office letterhead, says carriers should deny Snowden boarding because "the individual is highly likely to be refused entry to the UK."

The Associated Press saw a photograph of the document taken Friday at a Thai airport. A British diplomat confirmed that the document was genuine and was sent out to airlines around the world.

Snowden revealed top-secret documents about U.S. National Security Agency surveillance programs and is believed to be in Hong Kong. No warrants for his arrest have been issued.