The US government has warned American and foreign airlines that terrorists could try to hide explosives in toothpaste tubes on Russia-bound flights.
An official said it had information "specifically targeting flights to Russia", where the Winter Olympics will begin in the resort city of Sochi today.
The Department of Homeland Security said on Wednesday that, "out of an abundance of caution", it regularly shared relevant information with partners both at home and abroad.
"While we are not aware of a specific threat to the homeland at this time, this routine communication is an important part of our commitment to making sure we meet that priority," it said.
"As always, our security apparatus includes a number of measures, both seen and unseen, and DHS will continue to adjust security measures to fit an ever evolving threat environment."
US President Barack Obama's National Security Council said the disclosure had not affected existing guidelines about travel to Sochi. "If we should receive information in the coming days and weeks that changes our assessment of whether people should travel to Sochi, we will make that information public through the State Department's usual channels," spokeswoman Laura Magnuson said.
Peter King, chairman of the House subcommittee on counterterrorism and intelligence, said airlines and people attending the games should take warnings seriously. He declined to go into detail about the warning to carriers.
"Odds are nothing is going to happen, but the odds are higher than for any Olympics, I believe, that something could happen," King told CNN.
Stringent rules about liquids and toothpaste in hand luggage have been standard practice on US carriers after a string of thwarted plots in wake of the September 11, 2001 attacks.
Security at the Games has been a major concern following two deadly December suicide attacks in the southern Russian city of Volgograd. Adding to the concern is a stream of threats from Islamist militants in the vol atile northern Caucasus region.
Two US warships have arrived in the Black Sea and will stand ready to offer assistance in the case of a security emergency.
Additional reporting by Bloomberg