The Secretary of the Homeland Security Department said Thursday that a warning to airlines that terrorists could try to hide explosives in shoes was a routine advisory issued in response to the latest intelligence.

Secretary Jeh Johnson made limited comments on the threat during a news conference at Los Angeles International Airport. Johnson had toured the airport’s security operations and planned to meet later with law enforcement at a regional intelligence center.

“As you know, concerns about shoe bombs have been out there for years,” Johnson said. “Every once in a while we update our advisories, we modify our procedures, so we remain vigilant in dealing with the various potential threats that exist.”

A U.S. intelligence official told the AP that DHS released a notice to airlines reiterating that liquids, shoes and certain cosmetics were of concern. The warning was focused on international flights into the United States.

Johnson also commented on his decision Wednesday to withdraw a contract proposal asking a private company to give the government access to a nationwide database of license plate tracking information.

The proposal said Immigration and Customs Enforcement was planning to use the license plate data in pursuit of criminal immigrants and others sought by authorities.

“I think that any proposal of that nature should require a careful review as it concerns privacy, civil liberties concerns, at the senior levels of the department, including myself, so that’s why I did it,” Johnson said.

Johnson spoke to a crowd of reporters beyond the screening checkpoint area while flanked by six Transportation Security Administration officers. He emphasized multiple times in his opening remarks that he’d come to LAX to “express solidarity with my TSA colleagues.” The agency lost its first officer in the line of duty during a Nov. 1 attack at the airport by a gunman targeting the agency’s employees. Two other TSA officers and a traveler was wounded.

TSA is conducting a review of airport security policies as a result of the shooting. That’s in addition to a separate investigation into the shooting the airport’s expected to make public next month.

“I asked them (TSA officers) directly: ‘Tell me what more we can do,'” Johnson said. He said he agreed with TSA Administrator John Pistole’s decision to reject arming officers in response to the attack.

(AP)