A 25-year-old Jamaica Plain man was arrested by Braintree police last Thursday afternoon after suspicious activity led them to pull him over and a canine discovered heroin hidden in his vehicle.

William P. Mercado was charged with with possession of heroin with intent to distribute, failure to keep within marked lanes and having excessively tinted windows, Chief Russell Jenkins said in a statement.

Lucky, the department's drug sniffing Labrador Retriever, located several bags of heroin behind the fuse box of Mercado's car after he was stopped near the on-ramp to Route 93 South, Jenkins said.

Mercado originally seemed suspicious when he stopped at a business at Hancock and Plain streets and then weaved as he drove down Franklin Street.

Lucky was called to the scene after detectives conducting the traffic stop "made observations of items inside the vehicle, that coupled with Mercado’s answers to their questions, suggested that he may be in possession of narcotics," Jenkins said.