Dorchester Central Dispatched Station 6 (Hurlock), Station 21 (East New Market), & DCEMS PM600 units to the MVC with rollover. Ambulance 6 arrived on location to find 1 tractor trailer on it's roof with no patient. Ambulance Captain 6 established command and called for Haz-mat 1-1 and A heavy wrecker team. Ambulance Captain 6 transferred command to Chief 6 who confirmed. Haz-mat 1-1 arrived on location to pump off 2 saddle tanks and was released via command. Route 331 remained closed extended for investigation and clean-up.