The US Department of Homeland Security (DHS) has advised airlines to beware of any attempts to smuggle explosives onboard in footwear.
Homeland security officials did not indicate any known specific threat or plots, but said the warning focused on US-bound flights from abroad.
It is the second time in recent weeks that the US has warned of an increased threat of explosives on airliners.
In 2001, Briton Richard Reid attempted to blow up a flight from Paris to Miami with explosives hidden in his shoes.
“Our security apparatus includes a number of measures, both seen and unseen, informed by the latest intelligence and as always DHS continues to adjust security measures to fit an ever evolving threat environment,” the Department of Homeland Security said in Wednesday’s statement, reports the Associated Press.
The latest advisory comes just weeks after the US told airlines to be on the lookout for explosives hidden in toothpaste tubes on direct flights to Russia.
That warning, on February 6, came ahead of the Winter Olympics opening ceremony in Sochi.
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