At least 30 people were killed and 150 others injured in a powerful blast that went off Thursday night in the downtown area of Karachi, the largest industrial city in southern Pakistan, sources in Karachi told Xinhua.

People transfer an injured woman from the blast site in southern Pakistan's Karachi on Nov. 11, 2010. At least 30 people including 12 policemen were killed and 150 others injured in a powerful blast that went off Thursday night in the downtown area of Karachi, the largest industrial city in southern Pakistan. [Arshad/Xinhua]

According to sources, a building targeted by the blast was leveled to ground and many others were buried under the debris. The number of the people trapped in the collapsed building is estimated at 40.

Initial reports said that the blast took place at a building of the Pakistan Industrial Development Corporation (PIDC), but latest news coming in said that the blast occurred at a building of Crime Investigation Department (CID) where at least six terrorists from Lashkari-e-Jhangvi and a Taliban militant were detained inside in addition to some other criminals.

The blast took place at about 8 p.m. at the Club road in Karachi, a busy area in the city where many important building are located including the house of Sindh province governor, the residence of Karachi chief minister and the U.S. consulate.

Sources said that there was a fierce firing outside the CID building before the blast took place.