LAHORE, Pakistan (Reuters) -- At least 18 people were killed and up to 150 trapped on Wednesday when a factory collapsed near the eastern Pakistani city of Lahore, officials said, adding to a number of industrial disasters to hit the South Asian nation.

Rescue workers digging for survivors with construction equipment have recovered 75 injured people so far, said Mohammad Usman, a senior local government official who was on the scene.

Eighteen dead bodies have also been found, he said.

Around 150 people were feared trapped under the rubble after the building collapsed, said rescue worker Kashif Nazir at the scene.

No part of the four-floor building remained standing after the disaster, and hundreds of rescue workers were carefully picking through piles of concrete and bricks to find survivors.

"People have received phone calls from three or four people from inside the debris, so we cannot remove the rubble recklessly," said Usman.

The military was flying urban search-and-rescue teams to the scene, said a military spokesman in a text message.

"Army engineers have been immediately moved for the rescue operation," the message said.

The factory, located at an industrial site about 20 km (12 miles) south of the city, manufactured shopping bags. It was not clear what caused the collapse, though construction work had been going on there.

"My son is a daily wage laborer here. We can't find him among the dead or the injured, so I am just hoping that he will be recovered from the rubble safely," said Mohammad Ramzan, whose 24-year-old son Amin was missing.

Pakistan's construction sector suffers from poor oversight and developers frequently flout building codes.

In September 2012, 289 people burned to death in a fire at a garment factory in the southern city of Karachi. On the same day, a fire at a shoe factory in Lahore killed 25.

(Writing by Asad Hashim; editing by Gareth Jones)