Workers walk after a fire broke out at India's Serum Institute in Pune on Thursday. AFP

At least five people were killed in a fire that broke out on Thursday at a building under construction at Serum Institute of India, the world’s largest vaccine manufacturer, officials said. The company said the blaze would not affect production of the COVID-19 vaccine.

TV channels showed thick clouds of grey smoke billowing from the sprawling site in Pune, which is responsible for producing millions of doses of the Covishield coronavirus vaccine, developed by AstraZeneca and Oxford University.

"It is not going to affect production of the COVID-19 vaccine," a Serum Institute source told AFP, adding that the blaze was at a new facility being built on the 40-hectare campus.

Murlidhar Mohol, mayor of Pune city in southern Maharashtra state, said five bodies were found in the rubble after the flames were extinguished by firefighters.

Mahol said the victims were probably construction workers. He said the cause of the fire had not been determined and the extent of damage was not immediately clear.

People stand outside the Serum Institute after a fire broke out. AFP

Serum Institue of India's CEO, Adar Poonwala, said he was “deeply saddened” by the loss of life. He said there would be no reduction in vaccine manufacturing because the company has other available facilities.

The company said the fire was restricted to a new facility it is constructing to increase the production of COVID-19 vaccines and ensure it is better prepared for future pandemics.

It said the fire did not affect existing facilities making COVID-19 vaccines or a stockpile of around 50 million doses.

Images showed huge plumes of smoke billowing from the building and dozens of company workers in lab suits leaving the compound as firefighters worked to extinguish the blaze.

People watch as smoke rises after a fire broke out at Serum Institute in Pune. AFP

Serum Institute of India is the world’s largest maker of vaccines and has been contracted to manufacture a billion doses of the AstraZeneca/Oxford University vaccine.

Poonawalla said in an interview with The Associated Press last month that it hopes to increase production capacity from 1.5 billion doses to 2.5 billion doses per year by the end of 2021. The new facility is part of the expansion.

Of the more than 12 billion coronavirus vaccine doses expected to be produced this year, rich countries have already bought about 9 billion, and many have options to buy even more. As a result, Serum Institute is likely to make most of the vaccines that will be used by developing nations.

Agencies