A Nashville man whose vehicle broke down on Interstate 40 in Dickson County Saturday called police after one of his grandchildren made an unusual discovery. Agents with the 23rd Judicial District Drug Task Force say the child picked up a wrapped bundle of almost one pound of heroin that was just lying on the side of the interstate near the 178-mile marker of the eastbound lanes. An agent speculated the heroin might have been tossed from a vehicle out of concern over a possible traffic stop or even could have been intentionally left at a specific location along the busy interstate as a drop point for a transaction. The Nashville man, whose name was not released, said he pulled over when his alternator malfunctioned on his way home Saturday afternoon. The older of two grandchildren with him got out of the vehicle and picked up what appeared to be a wrapped bundle inside a zippered plastic storage bag. Fearing that it could be drugs or explosive materials, the man took the package from the child and threw it further from the road before calling police. A Dickson County Sheriff’s Office deputy notified the drug task force and an agent said the substance tested positive for heroin in a field test. The agent said it is very unusual to find that quantity of heroin in Dickson County and estimated its street value at $50,000-$60,000.