At least 18 people were killed and dozens of others injured Monday as a powerful blast in a truck rocked a crowded commercial area in Pakistan's southern city of Hyderabad, police sources said.

Police said the blast occurred in a truck loaded with gas cylinders that was parked at a truck stand at Halanaka, an area on the outskirts of Hyderabad, the second largest city in southern Sindh province.

The blast destroyed 10 roadside shops, hotels, two trucks and a nearby mosque. Electric polls were also damaged, suspending power supply to several parts in the area.

Senior Superintendent Police, Muhammad Ali Baloch told Geo television that 18 persons were killed in the blast.

Regional Police Officer, Fayyaz Leghari said that nature of the blast is not clear, but some eyewitnesses say gas cylinder or chemical on the trucks have caused the blast.

Leghari said preliminary investigation suggests that it was not an act of terrorism, adding that investigation in underway to determine cause of the blast.

Home Minister of Sindh Province Zulfikar Mirza also said that a gas cylinder may have caused the blast, which was followed by another blast.

The intensity of blast was multiplied as a transformer was present near the truck when it blew up, he added, saying investigations are going on to determine the real cause.

But a police officer did not reject possibility of an act of terrorism. Geo television quoted a police officer as saying that the police are also probing into the incident.

Ambulances were sent to the area to rush the injured to hospitals. Locals and police joined hands to remove bodies and injured to hospitals.

Doctors said that 10 injured are in critical condition at two main hospitals in the city. Several injured were also taken to private hospitals.

Paramilitary soldiers and police were deployed at the blast site and experts from bomb disposal squad collected evidence to determine cause of the blast.

Halanaka is a busy area where a large number of roadside hotels are located and drivers usually parked their trucks for eating.