Washington, Dec 25 (IANS) Air travellers carrying thermoses or coffee cups at US airports may be subject to extra scrutiny during this holiday season as such items could be used to conceal explosive materials, according to an official advisory.

Officials note no specific threat regarding thermos bottles and cups, but the warning to Christmas Eve travellers and others flying on airliners over the winter holidays comes as part of a broader official effort regarding airport and airline security, Christian Science Monitor reported.

‘Passengers travelling with insulated beverage containers can expect to see additional screening of these items using procedures currently in place, including X-ray screening, physical inspection and the use of explosives trace detection technology,’ states an advisory issued by the Transportation Security Administration (TSA).

US airports are expected to receive some 43 million travellers during the winter holidays, according to the Air Transport Association of America.

However, many travellers have complained about increased personal security measures at airports since last year’s Christmas Day airliner bomb attempt by a Nigerian man.

In response to terrorist threats, the TSA now gives airline passengers two choices: Get a full-body scan using low-dose radiation that shows a naked image – everything from head to toe. Or refuse the scan and have a TSA official run his or her hands over every part of your body.

At a White House briefing, chief counterterrorism adviser John Brennan outlined steps taken over the past year to increase security.

Among other things, gaps in analysis and data collection have been closed, the criteria used to create terrorist watch lists and ‘no fly’ lists have been revised, the Monitor said Friday citing Brennan.

Some 500 of the controversial ‘Advanced Imaging Technology’ scanning machines for passengers have been deployed at more than 75 US airports, and additional steps have been taken to screen cargo shipped by air or checked by passengers.

‘We are in a much better position today than we were last year at this time,’ Brennan said.

Still, authorities are taking no chances when suggestions arise of new means of attack – including the possibility of hiding explosives as part of the insulation in thermoses and beverage cups.

The new TSA advisory notes that such items are allowed – for now, at least – based on an assessment of risk. The advisory applies to thermoses and cups whether or not they contain any liquids.

It also reminds airline passengers that the ‘3-1-1 rules’ for liquids remain in effect for carry-on bags. This states that liquids or gels must be in containers holding no more than three ounces; that such containers must be placed in a clear, one-quart zip-lock bag; and that travellers are limited to one such bag apiece.

This latest announcement comes as part of stepped-up efforts to prevent a terrorist attack in the US during the holiday season, according to the Monitor.