India's southern state of Andhra Pradesh wrapped up rescue efforts on Thursday at a pharmaceutical manufacturing plant where an explosion the previous day killed 17 people and injured nearly 40, a senior state official said.

The state's worst such incident in recent years, Wednesday's blast took place at the 40-acre (16-hectare) unit of privately held Escientia Advanced Sciences in the Anakapalli district.

Nearly 40 people were injured and rescue operations had been completed, the official, Industries Secretary N. Yuvaraj, told Reuters.

Escientia did not immediately respond to a request for comment but government officials said they suspected an explosion in the chemical reactor.

Officials said they were scanning closed-circuit television footage and questioning the injured to decide if human error was responsible for the blast.

"Preliminary investigation shows ... there was some vapour leak that led to chemical reactions, which caused the explosion," added Yuvaraj, who identified the solvent involved as methyl tert-butyl ether.

In a post on X, Prime Minister Narendra Modi offered condolences to the relatives of the dead.

India, known as the pharmacy of the world, is home to many plants that make pharmaceuticals.

A fire in the same district last year in a unit of Sahithi Pharma killed two people and injured five.