An explosion that killed three people in an apartment building in Moscow was caused by gas-welding done by students producing medieval arms, the city's mayor Yury Luzhkov has said. The blast occurred on the 11th floor of the 22-storey building on Academic

Luzhkov says the restoration work will take up to three weeks.

The blast sparked a fire which then spread to the tenth and the twelfth floors causing the collapse of ceilings and walls. Four apartments were gutted.

“Several side panels collapsed, some of them fell out on cars parked near the house. The building itself is steady, the supporting structures have not been affected,” Luzhkov said.

Sixteen people were rescued from the building, among them a 14-year-old boy who was injured, but is reported to be in a satisfactory condition. He's been undergoing medical treatment.

Meanwhile, more than forty people who were evacuated from the building remain into temporary accommodation.

The explosion occurred in the early evening, before many people had returned home.