Pakistani police have revised the cause of a blast that killed 83 people on Saturday, saying a suicide bomber was behind the attack that pulverized a busy marketplace.

The explosion targeted Shiite Muslims in Hazara, on the outskirts of the southwestern city of Quetta, authorities said.

Police now say a suicide bomber, driving an explosive-laden water tanker, rammed the vehicle into buildings at the crowded marketplace.

The water tanker carried between 800 and 1,000 kilograms (1,760 to 2,200 pounds) of explosive material, Quetta police official Wazir Khan Nasir said.

Previously, police said explosives were packed in a parked water tanker and were remotely detonated.

The blast demolished four buildings of the marketplace, leaving dozens dead and 180 injured.

As of Sunday morning, no group had claimed responsibility for the attack.

The assault left some wondering what could stop the bloodshed in Quetta.

Zulfiqar Ali Magsi, the governor and chief executive of Balochistan province, told reporters Saturday that law enforcement agencies were incapable of stopping such attacks and had failed to maintain law and order in Quetta.

Pakistan, which is overwhelmingly Sunni, has been plagued by sectarian strife and attacks for years.