Mohammad Usman, the top administration official in Lahore who is coordinating the response to the disaster, said 102 people had been rescued, and that the focus of the operation remained the search for survivors.
Rescuers were using audio and video technology as they searched, he said. Cranes and machinery provided by the army were also being used.
The collapse occurred at the four-storey Rajput Polyester polythene bag factory in the Sundar industrial estate, about 45km southwest of Lahore's city centre.
The factory may have suffered structural damage in the Oct 26 quake which killed almost 400 people across Pakistan and Afghanistan, Punjab chief minister Shahbaz Sharif said.
"I have heard about the earthquake affecting the building, but according to labourers the owner continued to build an extension," he said.
“Some of the pillars of the building had been weakened in the earth quake, 22-year-old Navid said, adding that workers had informed the owner of the problems.
“The building caved in with a big bang and I fell unconscious on the ground, he said, adding that he had regained consciousness after some 15 minutes.
"I heard people screaming and shouting for help."
Pakistan has a poor safety record in the construction and maintenance of buildings.
At least 24 people died last year when a mosque collapsed in the same city, while more than 200 people lost their lives, mostly due to collapsed roofs, following torrential rain and flooding in 2014. AFP