Concerned about terrorist attacks at the Winter Olympics, the Transportation Security Administration has temporarily banned carry-on liquids, gels, aerosols and powders for travelers flying from the United States to Russia.

The Department of Homeland Security issued warnings Thursday to U.S. airlines that terrorists may try to conceal explosives in toothpaste tubes and cosmetic containers to disrupt this month’s games in Sochi, Russia.

A DHS official said that the agency does not know of a specific threat at this time, but House Homeland Security Chairman Mike McCaul said during a CNN interview on Wednesday: “The terror threat has been around for several days. I find it to be very specific and credible.”

He had been briefed that day by multiple intelligence agencies, according to his office.

McCaul added that Homeland Security is “taking a lot of precautions in terms of tightening up screening at the airports” to ensure that explosives will not be smuggled onto airplanes or into the Olympic village.

The DHS official declined to provide further details about the ban or the warnings, but said the department uses measures “seen and unseen” to protect Americans from ever-evolving threats, including intelligence gathering, random canine searches, temporary restrictions, and using federal air marshals and new technologies.

Russian Deputy Prime Minister Dmitry Kozak, who is responsible for the host nation’s Olympic preparations, told reporters that law-enforcement services in his country were on top of the security situation.

“All the information we have at this moment on threats and risks allows us to say that security at the Olympics will be provided,” he said, according to a report from the state-owned RIA Novosti.

As part of the new DHS security policy, passengers heading to Russia will have to check in personally with airline representatives at airports, as opposed to checking in online, through their mobile devices or at kiosks, according to an announcement from Delta Air Lines.

Airport screeners will still allow passengers to carry prescription medications on their flights, the announcement said.