A blast in an Indian pharmaceutical factory has killed at least 17 people with chemicals burning the skin off several of the 30 others injured, police said on Thursday.

The Hindu newspaper reported that the force of the blast had been so strong, it left severed body parts scattered around the site.

The fire broke out on Wednesday afternoon at a pharmaceutical unit in Andhra Pradesh's Anakapalli district.

District police superintendent M. Deepika told AFP that no one was left trapped inside the building and rescue operations were over.

"(There are) 17 dead and 34 injured," he said.

He added that investigators believe the blast was caused by a gas leak.

Local police official M. Buchaiah told the Indian Express daily that those caught in the blast suffered horrific chemical burns.

"It was horrible, heartbreaking," he told the paper, describing the pain people suffered as those who survived were carried to ambulances.

"They were screaming before they lost consciousness".

It was not immediately what had sparked the explosion.

Prime Minister Narendra Modi on Thursday said he was "pained by the loss of lives", in a post on social media, announcing compensation of $2,380 to the families of those killed.