A powerful explosion Sunday destroyed a bank and dozens of apartments above it in Nigeria's commercial capital, and relief workers reported at least 30 killed and many more trapped.

The blast scattered money from the bank, setting off looting and bloody fights as hundreds of young men grabbed wads of cash and then battled over them.

Authorities did not immediately say what caused the blast. Many in the neighborhood said it was part of a bank robbery attempt.

"We don't know what happened ... but our men are already investigating," police spokesman Emmanuel Ighodalo said.

The blast occurred about 12:30 p.m. on Lagos Island, a crowded high-rise district of banks and other businesses packed side-by-side with densely populated residential neighborhoods.

The explosion could be heard for miles and sent up a tower of smoke.

The explosion caused the four-floor bank building to collapse and heavily damaged two adjacent buildings.

Three floors of apartments came crashing down on top of the bank. An Associated Press reporter at the scene and the hospital saw 10 badly crushed bodies, including one corpse that appeared to be that of a child.

A Red Cross official, who refused to give his name, said more than 30 bodies had been recovered by mid-afternoon. "I believe a lot more people are still trapped," the official said.

Resident Omololu Kassim, who was helping carry away the victims, said he saw 40 dead and as many injured. Local radio put the death toll at 50 or more.

Many residents of the neighborhood had been at church, preventing an even higher death toll.

Police dispelled the crow of looters and forced back crowds of thousands of onlookers. Cranes and other heavy equipment moved in to lift heavy concrete slabs.

Crowds wailed as searchers pulled out mutilated bodies. Ambulance drivers fought to navigate narrow streets and push through the throngs to get to victims.

Lagos Island is one of two islands that, with the mainland, make up this city of 12 million. Congestion on the island has sent many businesses moving to other parts of Lagos in recent years.

On Jan. 27, 2002, a series of explosions at an army munitions depot in Lagos killed more than 1,000 people.