By Keith Coffman

DENVER (Reuters) - A routine police traffic stop in the state of Colorado led to the discovery of 220 pounds (100 kgs) of cocaine with a street value of $10 million in the rental car of a California couple, according to police.

Mark Bailey and Lisa Calderon, both of Sylmar, California, were arrested on Sunday in the city of Pueblo on suspicion of cocaine possession, Deputy Police Chief Andrew McLachlan said.

"This is definitely the largest cocaine seizure in our department's history," McLachlan told Reuters.

McLachlan said a patrol officer was tipped off by an off-duty detective to a car making an illegal lane change about 115 miles south of Denver.

The north-south highway has long been a drug-smuggling corridor, he said. When the officer pulled over the rented Chevrolet Malibu, he discovered that Bailey's California driver's license had been revoked.

Bailey, 37, told the officer he owned an auto body shop in California, and was en route to Iowa.

The officer became suspicious because when Calderon, 35, was questioned she appeared nervous. She said the pair were going to visit her brother in Iowa but couldn't say where, police said.

When the officer noticed that the back of the car appeared to be weighed down, he summoned a drug-sniffing dog and its handler to the scene, McLachlan said.

The pair was arrested after a search of the trunk uncovered four black duffel bags stuffed with bricks of cocaine.

(Editing by Dan Whitcomb and Cynthia Johnston)