Two people were killed and two were injured in an explosion in Shanghai's Pudong New Area yesterday.

The blast happened about 3:20pm in a two-story residential building in Sanlin Town.

The explosion was powerful enough to destroy the building's roof and half of the structure collapsed.

A man and his son, who installed and repaired air conditioners, were killed in the blast. They rented an apartment on the first floor. Another man and his daughter, who live on the second floor, were injured. The father suffered cuts on his head while his 21-year-old daughter was seriously injured.

An acetylene cylinder was found burned in the debris and residents said they suspect the father and son ignited the flammable gas, which triggered the explosion.

Residents living opposite the building said that they heard a big bang and felt their homes shake at 3:20pm. They saw heavy smoke and flames from the opposite building.

The injured man said he was sleeping while his daughter, a university sophomore, was doing homework when the blast occurred. He said the floor collapsed.

He said he walked out from the debris and heard his daughter crying for help. He then returned with some neighbors to remove the debris and rescue his daughter.

His wife was at work at the time. She came to the hospital after the accident.

She cried and said the family had planned to travel back to their hometown to celebrate Chinese New Year. Now they will have to stay in Shanghai.

The Pudong government said the cause of the accident is still being investigated.