Even with three more explosive-detecting dogs coming to Metro, the chances that any rider will ever see a dog team in action are slim.

But yesterday at a congressional hearing where a program to train dogs for transit was announced, three dogs trained by federal agencies showed a room full of legislators and government employees how they sniff their way to concealed explosives, people, narcotics or chemical agents in the interest of homeland security.

Metro is one of 10 U.S. transit systems that will receive three explosive-sniffing dogs this year from the Transportation Security Administration.

The announcement was made before a subcommittee of the House Homeland Security Committee. Rep. Mike Rogers (R-Ala.), chairman of the subcommittee, said he believes there is a shortage of trained dogs, which are used to help protect the country against terrorism.

To demonstrate for the subcommittee, Quan, a yellow Labrador retriever -- one of about 500 explosive-detecting dogs trained by the Bureau of Alcohol Tobacco, Firearms and Explosives -- stuck his nose into four buckets. Three were filled with distracting odors, such as tea, sugar or nondairy creamer. A fourth bucket contained a small amount of plasticized RDX explosive.

When Quan smelled the explosive, he sat. His handler, special agent Craig Chillcott, rewarded him with a dog biscuit.

Skeet, a black Labrador retriever, one of nearly 1,200 dogs trained by U.S. Customs and Border Protection, found explosives in a woman's briefcase and was rewarded with a rolled-up towel. Canine instructor Mike Merickel said Skeet's motivation is a game of tug of war, "with a lot of hoppin' and hollerin'."

Merickel and Skeet recently were sent to Detroit for three weeks after July's London train bombings to search buses and trains. The Transportation Security Administration, which has 345 explosive-detecting dog teams deployed at 66 airports, is making its first major foray into mass transit.

Three law enforcement officers from each of the 10 selected transit agencies will travel to Lackland Air Force Base in Texas, where they will be matched with dogs and undergo 10 weeks of training.

Rogers questioned whether 30 dogs, for a nationwide system of commuter rails and buses that transports 14 million people daily, would make a big difference. "That seems like kind of an ominous challenge, doesn't it?" Rogers said. With the new dogs, Metro's canine patrol will be about 13 for 86 stations.

"We see the explosive-detection dogs as another tool in our security toolbox," Metro spokeswoman Cathy Asato said. She said the dogs will join forces with police officers and cameras.

Quan, a bomb-sniffing Labrador retriever, inspects packages at the Cannon House Office Building as part of the announcement of a new canine program.Quan sits after he smells an explosive during a demonstration for a House subcommittee.