At least a dozen others are feared trapped under the debris, they said.
Firefighters were trying to douse the flames when the the factory collapsed in Mushtaq Nagar, trapping 15-20 people, police officials said.
"Four bodies have been pulled out," Deputy Commissioner, Ludhiana, Pradeep Aggarwal said.
Three victims have been identified as Inderpal Singh, Fire Officer Simaon Gill and fireman Puran Singh. Efforts are being made to ascertain the identity of the fourth person, he said.
Earlier, it was reported that three firefighters had died in the incident.
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Earlier in the morning, at least 15 fire tenders were rushed to the spot to control the fire.
Personnel of the National Disaster Response Force (NDRF) and Army experts are being aided by local authorities in the massive rescue operation. Earth-moving machinery is being used to clear the debris.
Senior district administration and police officials are present at the site.
Punjab Chief Minister Amarinder Singh said he was "shocked and saddened" by the factory collapse incident.
"Shocked and saddened at the Ludhiana factory collapse. Have asked district administration to extend all help to NDRF in rescue operations," he tweeted.
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