LAHORE, Pakistan (AFP) - Around 100 people, including women and children, were feared trapped Monday when a building collapsed in Pakistan's second largest city of Lahore, witnesses and an emergency official said.

Witnesses said about 150 people normally worked at the factory in the building in the eastern city's congested Multan Road neighbourhood. Officials said a gas cylinder explosion could have caused the accident.

"Initial reports say more than 100 people were present in the factory when it collapsed, possibly because of a gas cylinder explosion," rescue official Mohammed Aamir told AFP.

One body had been pulled out of the rubble and at least six injured people, most of them young children, rescued, he said.

The factory used to manufacture veterinary injections, Aamir said.

An AFP photographer saw women and children being taken out with injuries and covered in dust.

Witnesses said that up to 150 people normally worked at the factory.