U.S. issues warning about shoe bombs on airplanes bound for U.S

U.S. Department of Homeland Security emblem is pictured at the National Cybersecurity & Communications Integration Center (NCCIC) located just outside Washington in Arlington, Virginia September 24, 2010. REUTERS/Hyungwon Kang

WASHINGTON (Reuters) - U.S. authorities issued a warning on Wednesday to airlines flying to the United States to watch out for militants who may have hidden bombs in their shoes, U.S. government sources said.

The warning came from the Department of Homeland Security, the sources said, and it is consistent with concerns security agencies have about militants trying to smuggle explosives onto airplanes in shoes, cosmetics or liquids.