A fire has broken out at a COVID-19 manufacturing plant in India, sending huge clouds of grey smoke into the sky.

According to reports, the fire broke out at the Serum Institute of India (SII), the world's biggest vaccine maker, where millions of doses of the Oxford/AstraZeneca vaccine are being manufactured. Local reports said that the blaze was at a construction site at the large facility, with a source close to the plant telling the BBC the fire will not affect the production of the COVID vaccine. Doses produced at the plant will go to India and many other low and middle-income countries.

The site in Pune, in the western state of Maharashtra, is also preparing to produce the vaccine being developed by the U.S. company Novavax Inc. Pune's fire office told Reuters news agency five fire trucks had been sent to the site. There was no immediate word on any casualties, nor on the cause of the fire.

This month Indian regulators approved two vaccines, Covishield - the vaccine developed by AstraZeneca and Oxford University - and produced by the Serum Institute, and Covaxin, made by Bharat Biotech, based in Hyderabad.

India has launched one of the world's largest vaccine rollouts with the aim of immunizing 300 million people by August. The country has registered more than 10.5 million COVID cases, the second-highest in the world, and 152,000 deaths, according to the World Health Organization COVID tracker.

Smoke rises after a fire broke out at India's Serum Institute in Pune on January 21, 2021Getty

Prime Minister Narendra Modi kickstarted the campaign with a national televised speech with the first dose given to a health worker at the All India Institute of Medical Sciences in Delhi. Modi urged citizens to get the vaccine and told people not to believe any "rumors about the safety of the vaccines".

According to a survey on vaccine hesitancy, which involved more than 8,000 people and was carried out by the polling company Local Circles, 69 percent of Indians are hesitant about receiving the vaccine. Frontline healthcare workers, police and the army have been given priority, with those over 50 and with co-morbidity conditions to follow, all free of cost.

The SII has received billions in pre-orders from countries around the world desperate for the vaccine. The Indian government is negotiating how much stock to release for export, given fears that it could lead to a domestic shortage. India has already exported COVID vaccines to Bhutan and the Maldives, as well as millions of doses to Bangladesh and Nepal. The country plans to offer 20 million doses to neighboring countries in South Asia, followed by Latin America, Africa and Central Asia.

Videos and photos posted to Twitter showed smoke from the fire could be seen for miles across Pune. An SII representative did not immediately respond to an email seeking comment.