A fire broke out Thursday at a building under construction at Serum Institute of India, the world’s largest vaccine manufacturer, possibly affecting its future expansion of COVID-19 vaccine production.

Firefighters were extinguishing the flames, the fire office in Pune city in southern Maharashtra state said. The cause of the fire and extent of damage were not immediately clear.

Television channels showed a huge cloud of grey smoke above the site in Pune in the western Indian state of Maharashtra on Thursday.

The SII is manufacturing millions of doses of a vaccine developed by Oxford University and AstraZeneca for India and many other low- and middle-income countries.

The company is also getting ready to produce a vaccine being developed by the United States company, Novavax Inc.

Reports said the blaze was at a new plant under construction at the large facility.

Pune’s fire office told Reuters news agency five fire trucks had been sent to the site. “We have no other information … on the extent of the fire or whether anyone is trapped,” an official said.

There was no immediate word on any casualties, nor on the cause of the fire.

“It is not going to affect production of the COVID-19 vaccine,” a source at the Serum Institute told AFP news agency.

Earlier this month, Indian regulators approved two coronavirus vaccines – Covishield, produced by the SII, and Covaxin, made by local firm Bharat Biotech.

India began one of the world’s biggest vaccine roll-outs on Saturday, aiming to vaccinate 300 million people by July with both Covishield and Covaxin.

Many other countries are relying on the SII to supply them with the vaccine.

India began exporting the vaccines on Wednesday, with the first batch sent to Bhutan and the Maldives, followed by two million doses to Bangladesh and one million to Nepal.

The country plans to offer 20 million doses to its South Asian neighbours, with Latin America, Africa and Central Asia next in line.

The SII also plans to supply 200 million doses to Covax, a World Health Organization-backed effort to procure and distribute inoculations to poor countries.