CRANBURY, N.J. (AP) - State police seized more than $5 million US in cash Thursday from a tractor-trailer found idling unattended for two days on the shoulder of a roadway, authorities said. The driver, Salvadore Delarosa, 46, of San Bernardino, Calif., was arrested on a money laundering charge. "The cash is the proceeds of illegal conduct, possibly narcotics activity, but that still remains under investigation," Attorney General Peter Harvey said. Investigators have not yet determined the exact source of the money. Delarosa was seen near the vehicle Thursday, said state police spokesman Capt. Al Della Fave. After questioning him, authorities found the cash in six cardboard boxes in the sleeping berth behind the cab. Each weighed about 45 kilograms; the bills were mixed denominations, Della Fave said. Della Fave said a preliminary count put the total at about $5.3 million, which would make it the largest money seizure in state history. The truck was registered to a California company, but it was not immediately clear if Delarosa was employed there.