The United States Homeland Security Department has issued stern warnings to airlines flying to Russia for the Winter Olympic Games that terrorists could potentially try to smuggle explosives on board hidden in tubes of toothpaste.

The threat was passed onto airlines that have direct flights to Russia, including some that originate in the United States, according to a law enforcement official speaking Wednesday on condition of anonymity because he was not authorized to discuss details of the warning.

The unnamed official was quoted as saying that the airlines have been advised and issued warnings that explosive devices could be put together mid flight or upon arrival at the Olympic park.

The department said in a statement that the United States “isn’t aware of a specific threat to the homeland at this time.” It also stated that the department “regularly shares information with domestic and international partners, including those associated with international events such as the Sochi Olympics.”