LONDON- These days, passengers on the London Underground with backpacks undergo a new kind of scrutiny: Dogs sniff their bags, hunting for explosives in a bolstered effort to prevent terrorists from striking again.
Police dogs are roaming the capital's vast subway network for the first time, deployed in the aftermath of the July 7 suicide bombings on three London subways and a double-decker bus. While dogs have been used on the train to Heathrow airport and at select stations, the animals have never before been present throughout the system.
"They're way more reliable than any machine in existence," Transport Police spokesman Donal O'Reilly said Wednesday. "They're moving about on quite a regular, and what seems like _ at least to the traveling public _ a random basis."'
So far 28 dogs, mostly Labradors and Spaniels trained to detect bomb-making materials, are working alongside police in stations and aboard trains in the network that serves 3 million travelers a day.
Teams of two or three animals work with a sergeant and 12 other officers. As passengers enter station turnstiles, they pass through two lines of officers with a dog on each side. Travelers with backpacks are asked to remove them "and the dog has a sniff," O'Reilly said.
If the dog freezes or abruptly lies down, that's a sign that something might be amiss.
For some travelers, the dogs are a comfort.
"They're living, breathing beings, and that makes me feel more safe," subway rider Van Emden said at the Chancery Lane station in central London.
But others are concerned that 28 dogs can't possibly handle the sprawling Underground, which covers 520 square miles.
"There's just not enough of them," said subway rider Mark Maynard. "They could get lucky, but if anyone wants to plant a bomb, they'll probably do it anyway. Chances are there might not be a dog nearby."
Also, experts say some types of explosives are difficult for dogs to detect _ including TATP, or triacetone triperoxide.
Traces of TATP, which shoe bomber Richard Reid used in his failed 2001 attempt to blow up an airplane, reportedly were found in the apartment of Egyptian biochemist Magdy el-Nashar during raids last week in the northern city of Leeds, hometown of three of the four suicide bombers. The Egyptian government said Tuesday that el-Nashar, who taught at Leeds University and is wanted for questioning by Britain, had no links to the July 7 attacks or to al-Qaida.
Since the bombings, police have conducted numerous station evacuations, most triggered by travelers who briefly walked away from their bags. Frustrated by the rash of evacuations, Policy Exchange, a London think tank, this week urged lawmakers to make leaving luggage a criminal offense.
"It's time to acknowledge that leaving bags unattended is not simply a nuisance. It can cause panic and it diverts valuable policing resources," said Roy Ramm, former head of Scotland Yard's organized crime division.
So far, the dogs _ elite animals with experience securing royal visits and other high-profile events _ haven't turned up anything suspicious. But with commuters still jittery after the bombings, which killed at least 56 people and wounded 700, few Londoners have bristled at their presence.
"After what's happened recently, people find them reassuring," O'Reilly said. "People completely unsolicited have been coming up to the teams and saying, 'Thank you very much _ it's so good to have you here.'
"And the dogs are incredibly cute," he said. "Everyone wants to play with them."