The accident happened as the Hyderabad to Bangalore express was passing through Kurnool district in the state of Andhra Pradesh at about 0100 (1930GMT Friday).

The train was travelling at about 90 km/h (55mph) when at least seven carriages overturned and a small number left the track completely.

"So far we have 18 dead. I asked my officials at the site about the cause of the mishap - they said they are still ascertaining it," Railway Minister Nitish Kumar told reporters earlier in New Delhi, according to French news agency AFP.

Another crash victim has since died in hospital, rail authorities said.

Relatives desperately searched for loved ones among the bodies

At least 70 passengers are reported injured, and the toll is likely to rise as some carriages have yet to be cut open, AFP said.

About 30 passengers are at local hospitals, while the remainder are being given first aid.

Emergency staff have cleared the track to make way for other trains, railway authorities said.

Medical teams hurried to the crash site from Gooty railway station, 15km (10 miles) away.

It is still unclear what caused the accident - the fifth on India's railways this year.

Accident record

The poor state of many tracks has led to a number of serious accidents on India's railway system, one of the world's largest.

INDIA'S RAILWAYS

India's last major derailment was on 10 September, when at least 118 people died after a train jumped the tracks in eastern Bihar state Last year, there were 253 accidents in India, in which 120 people were killed 2,400 people have died in rail accidents over the past five years Most deaths occur in collisions, usually caused by signalling faults Indian Railways - with 1.6 million staff - claims to be the world's largest employer

At least 118 passengers died in September near Bihar's Rafigung station when the Delhi-bound Rajdhani Express went off the tracks and several carriages fell off a dilapidated railway bridge into a swollen river.

Many of India' one billion-strong population rely on the country's 63,000 km (40,000 mile) rail infrastructure, the second largest in the world.

Indian Railways runs almost 14,000 trains carrying more than 13 million passengers a day, but has about 300 accidents every year.

Transport experts say that an increase in traffic and lack of modernisation have made the rail system vulnerable, but authorities say the accident rate has dropped to 0.57 per one million km travelled in 1996/97 from 5.5 in the early 1960s.