The death toll in a massive explosion on a state-owned gas pipeline running through southern India has risen to 19, officials said Sunday, while police confirmed a case of negligence was filed against the company.

The death toll in a massive explosion on a state-owned gas pipeline running through southern India has risen to 19, officials said Sunday, while police confirmed a case of negligence was filed against the company.

A senior official from the East Godavari district of Andhra Pradesh state, where the blast occurred Friday, told AFP that the death toll was expected to rise further as some of the injured remained in critical condition.

"19 people have died so far, of the 17 injured six people have suffered 80 percent burns," Vijay Kumar, a senior Andhra Pradesh police official, told AFP on Sunday.    

The cause of the fire on the 18-inch (45-centimetre) pipeline owned by the Gas Authority of India Limited (GAIL), which gutted scores of huts in the coastal area, is still being investigated by the state authorities.

Police said a case of negligence has been filed against GAIL based on a complaint from a local state official.

"The initial complaint from the revenue officer of Nagaram (the affected village) has been registered and a case of negligence under various sections of law has been filed," Kumar told AFP in a phone interview, adding that no one had been arrested so far.  

GAIL is the country's largest state-owned natural gas processing and distribution company, and the damaged pipeline, the gas supply to which was cut off after the explosion on Friday, is used to transport pressurised natural gas for a power plant.

Witnesses contacted by phone told AFP Friday that angry locals had entered an office belonging to GAIL near the site of the accident, pelting it with stones and vandalising property.

Some newspaper reports said that villagers had complained of negligence as the pipeline had become rusty, while other reports said a stove in the area might have ignited gas that had leaked from the structure.

The Andhra Pradesh government has ordered an enquiry and will develop an action plan to avoid similar accidents in future, state Chief Minister N. Chandrababu Naidu said after the accident on Friday.

Earlier this month, six people were killed by a poisonous gas leak at one of India's largest government-owned steel plants in central Chhattisgarh state.

But Friday's incident was the most deadly to hit India's energy sector since last August, when 28 people were killed in a fire at an oil refinery in nearby Visakhapatnam, the largest city in Andhra Pradesh.

India's biggest offshore gas fields are located in the Bay of Bengal to the east of Andhra Pradesh.