A powerful blast took place in Pakistan's largest city of Karachi on Thursday. At least 30 people have been killed, with 150 other people injured. As Damion Jones tells us, the explosion is the area's second-biggest in the last six months.

Sources say a building targeted by the blast in Karachi was completely leveled, while many others were buried under the debris. The number of people still trapped in the collapsed compound is estimated at 40.

The blast occurred at a Crime Investigation Department complex, where at least six terror suspects from the Lashkari-e-Jhangvi network and a Taliban militant were detained, in addition to numerous others.

The explosion went off on Club Road at about 8 PM, in a busy downtown area where many important building are located, including the house of Sindh Province's governor, the residence of Karachi's Chief Minister, and the US Consulate.

One elderly man frantically described the moments before the boom.

Abdur Rab, Explosion Eyewitness, said, "I was getting the building whitewashed. The worker had just finished his work, and I was paying him. Suddenly, I heard gunfire that went on for about three or four minutes. Then an explosion rocked the area. We ran into our homes."

Another eyewitness says the blast was so huge that it left a 10-feet-deep crater at the site, and all nearby buildings were seriously damaged.

Police sources add that that the explosion was caused by an incendiary-device-laden truck.

Authorities rushed to the scene and sealed off the area shortly afterward. Rescue operations are under way.

The Pakistan Taliban immediately claimed responsibility for the attack. The extremist organization also threatened to target the President's house in its next assault.