At least 17 people were killed and 40 more were injured in an explosion at a pharmaceutical firm in southern India.

The blast ripped through the factory and sparked a fire at the 40-acre manufacturing unit of Escientia Advanced Sciences in Andhra Pradesh on August 21.

There were reportedly 387 employees working two shifts at the plant. Many of them escaped as they were out during lunch break, but dozens were still caught in the blast.

Harrowing footage shows an employee hobbling out of a bus at a hospital. He had severe chemical burns as his skin appeared to peel off. Other injured individuals followed behind him sporting various injuries.

Industries Secretary N. Yuvaraj told news agency Reuters that rescue operations have concluded.

He said: 'Preliminary investigations show there was a vapour leak that led to chemical reactions, which caused the explosion.'

The factory began operating in 2019 and produces intermediate chemicals and active pharmaceutical ingredients.

State officials have ordered a probe into the explosion.

In a statement, Indian Prime Minister Narendra Modi expressed his condolences to the families of the deceased.

He said: 'Pained by the loss of lives due to a mishap at a factory in Anakapalle. Condolences to those who lost their near and dear ones. May the injured recover soon. Compensation will be given to the next of kin of each deceased.'

The facility is located in an industrial zone known for many mishaps due to lax safety regulations.