Los Angeles ? Some travelers at Los Angeles International Airport and John F. Kennedy International Airport in New York will be searched for weapons and explosives using a new scanner that peers through their clothes and creates an image of the person’s body, federal officials announced Thursday.

The sophisticated technology, called millimeter wave imaging, might prove to be a more effective way to check travelers for guns, knives, bombs and dangerous materials than pat-down searches. But it has raised questions by privacy and civil-rights advocates, who say the screening process amounts to a virtual strip search.

Millimeter wave pictures are white and dark gray. Although they are somewhat fuzzy, they are detailed enough to reveal such features as breasts and body anomalies.

Transportation Security Administration officials said at least 30 more scanning devices will be purchased this year for use at other airports.

If passengers don’t want to go through the scanner, they will be subjected to other screening measures, including pat-down searches.