At least three people were burnt to death, while eight others were injured when a fire broke out at a pharmaceutical factory in Uttar Pradesh's Muzaffarnagar district, police said Friday.

The fire broke out Friday morning at the Meghna Factory, which was also involved in processing drugs for India's prominent drug maker Ranbaxy in the Mansoorpur industrial area of Muzaffarnagar, about 350 km from here, they added.

'Though the exact cause behind the incident is yet to be ascertained, preliminary investigations reveal the fire could have taken place due to a short-circuit in the factory,' Muzaffarnagar police chief Praveen Kumar told IANS over telephone.

According to Superintendent of Police (City) Rajiv Mehrotra, the body of two labourers were recovered while the fire was being doused and the third body was found afterwards.

Even as police ruled out the possibility of anyone being trapped inside the factory, labourers said two of their colleagues were still missing.

Accusing the factory authorities of not having proper fire fighting measures at the factory, the workers held protests and also resorted to vandalism.

According to police, the condition of four of the eight injured is critical.

As many as six fire tenders were pressed into service to control the blaze and it took them over three hours to douse the flames, police added.

'Chemicals stored at the factory fuelled the fire and it took more than three hours to put out the blaze,' Deputy Superintendent of Police Dev Karan said.