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(CNN) -- The United States is advising airlines with direct flights serving Russia to be aware of the possibility that explosive materials could be concealed in toothpaste or cosmetic tubes, according to a law enforcement source.
The source emphasized on Wednesday that there was no known threat to the United States, but the notice to U.S. and international carriers is based on new intelligence information ahead of the start of the Olympics in Sochi this week.
"It's real. It's real and we got very good information," a government source, who also did not want to speak for full attribution, told CNN. "It's based on a credible source. We're taking it seriously so are other countries taking it very seriously."
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The assumption is the threat would be on a departing flight from Russia, that source added.
The Homeland Security Department said in a statement that "out of an abundance of caution" it routinely shares "relevant information" with domestic and international entities, "including those associated with international events" like the Sochi Olympics.
Russian transportation officials this week banned liquids in airline carry-on luggage, according to a report from the Russian news agency RIA Novosti.
Rep. Peter King, chairman of the House Homeland Security Committee's subcommittee on Terrorism and Intelligence, said on CNN's "The Situation Room" that Americans, the airlines and those at the Olympics should take the threat "very seriously."
King, New York Republican, believes that the athletes and American spectators are "reasonably safe," but noted that he would not go himself.
"Just as a spectator, I don't think it's worth the risk. I mean, odds are nothing is going to happen, but the odds are higher than for any other Olympics, I believe, that something could happen," he said.
King said he has some confidence in how the Russians are handling security, but "really not enough because they are not sharing enough intelligence" about what's happening inside the country.
"We are getting some information about what's happening outside of Russia, some external threats, that type thing, or potential threats. I don't want to overstate that, he said.
He noted a "ring of steel right around the Olympics itself" but said "there's a real cause for concern" about getting to Sochi and surrounding areas.
The Obama administration has not indicated it is not safe to travel to the Olympics.
Secretary of State John Kerry, in an exclusive interview with CNN's "The Lead with Jake Tapper" before the toothpaste alert broke, said that "anybody who wants to go to the Olympics, which are just a great event, should go. And we're not telling people not to go."
Kerry added that people should be alert and take precautions, advice he says has been requisite since the 9/11 attacks.
"We've got a new consciousness about this," he said.
A senior administration official said that it would make any information public through the State Department should it receive information that "changes our assessment of whether people should travel to Sochi."
Matthew Olsen, a top U.S. counter-terrorism official, highlighted concern in testimony to Congress on Tuesday about whether Muslim fundamentalists in disputed regions of Russia -- or other groups -- could launch attacks on selected targets.
"There are a number of specific threats of varying degrees of credibility that we're tracking," he said. "And we're working very closely with the Russians and with other partners to monitor any threats we see and to disrupt those."
Terrorism experts say that airlines continue to be a target of terrorists wishing to make a spectacular impact with an attack. The focus since 2001 has shifted from hijackings to bombs, especially those that might be hidden in luggage.
U.S. authorities are also mindful of creative package or other novel ways to conceal explosives. For instance, a failed attempt to blow up an overseas flight heading to Detroit on Christmas Day in 2009 involved a bomb concealed in a passenger's underwear.
Shortly after 9/11 a man was convicted of trying to blow up a transAtlantic flight with explosives hidden in his shoes.
CNN's Jim Acosta, Ten Barrett, Evan Perez and Jake Tapper contributed to this report.