Police next week plan to roll out another anti-terrorism tool designed to stop bombers from attacking the city's subway system: portable explosive detection devices sometimes used at airports.

About a dozen high-tech detectors by various manufacturers — some resembling handheld vacuum cleaners, others the size of fax machines — will be positioned at subway entrances where officers conduct random bag searches, officials said Friday.

Instead of searching by hand, the officers will swab the outside of bags. The detectors can analyze the swabs for traces of explosives within a few seconds, police said.

"It's a much less intrusive means of inspection," said Inspector Michael Coan, a spokesman for the New York Police Department.

The devices are being tested to determine whether they will be put into regular use.

One of the devices being tested, the Smiths Sabre 4000, can detect evidence both of traditional explosives like TNT and of homemade fertilizer bombs, according to the company's Web site. The department paid between $25,000 and $50,000 for each detector, Coan said.

An estimated 4.5 million passengers ride the New York subway on an average weekday. The city began random subway searches in July following the London train bombings.