MARSHALLTOWN, Iowa (AP) _ J.R. is the nation's top dog in sniffing out drugs.

The Marshalltown police dog and his handler, Officer Melinda Ruopp, won the 2004 U.S. Police Canine Association national championships in Bay St. Louis, Miss.

J.R. earned a perfect score for his vehicle search, and a near-perfect for his building search. The performances made him the overall champion in narcotics detection.

``That dog is extremely reliable,'' police Sgt. Brian Batterson said.

J.R. has sniffed out drugs around Marshalltown for more than five years and has cracked some big cases. One time, a canine team searched a wooded area for two hours without finding anything. Then J.R. started digging and found five garbage bags full of marijuana estimated to be worth more than $100,000.

Ruopp said she trained the dog to detect narcotics by leaving a dog toy in a sack with marijuana for a few days and then hiding the toy for J.R. to find. The dog eventually associated the game with the scent, not the toy, and then learned the scent for other drugs, such as methamphetamine and cocaine.