The categorical warning to IOC officials, on August 6, came during the Oil Security Council meeting held in Guwahati by the Assam police.

The latest warning, police officials say, followed a number of unanswered letters and reminders from the Nagaon officials to IOC managers at Guwahati, Noonmati and Thekeraguri. A file at the district administration's office is proof of the one-way communication.

On August 11 around 4 am, following a loud explosion, menacing flames engulfed the depot's seven tanks containing 1,600 kilo litres of petrol, diesel and kerosene. More than 63 hours and 70 fire-tenders later, the fire continues toblaze.

Though forensic experts are yet to begin investigations, police is certain the fire was caused by a bomb planted on one of the tanks. Dismissing the rocket or missile theory, deputy commissioner Abbasi, said, "A rocket would have caused a circular hole. This was a bomb, probably a time device."

Pointing at the square hole in the 10 mm thick metal wall, just next to the tank's circular staircase, another official said, "The angle of the crater could not have been caused by anything that was fired because the other tank would have obstructed its path; also the height of the crater is not more than eight feet while the boundary wall, from where the alleged rocket was fired, is at least 12 feet high."

On August 10, construction at the oil depot was on till 5 pm. And besides the labourers, about 50 truckers and loaders were inside the depot till 9.30 pm. "It could have been anyone," the police official said, "a militant could have entered while activity was on or it could be an inside job."

Inaddition to the seven security personnel from the Directorate-General of Rehabilitation, the oil depot has 13 employees.

"While we had strengthened the security outside -- check-posts and regular patrolling -- we have been repeatedly asking them to get Central Industrial Security Force (CISF) personnel for their internal security," a senior district official said.

Less than an hour before the explosion, a sub-inspector from Raha police station visited the depot on a routine check and signed the register at the entrance gate.

In March last year, the Nagaon DC informed IOC's general manager at Noonmati refinery of the threat and advised him to hire two platoons of CISF for the Thekeraguri depot. This was followed by a reminder a month later that "the police feared sabotage and that their depot's security was inadequate."

Another letter was sent in September 1997. Written communications were followed by meetings at the district and state levels: In July, Nagaon's additional superintendent of police(security) met the depot's officials to inform them of ULFA's threat to all oil installations in Assam and asked them to beef up their security.

"We have been warning them of their two oil depots -- Thekeraguri and Lamding," a senior official said. Warnings to Lamding oil depot went unheeded till about a month back when, following a demand note to the manager, the oil company hired a platoon of home guards. "At Thekeraguri there was no threat to any individual so our warnings were ignored," the official added.

The oil company's executive director Sachdeva said, "IOC is the largest tax and excise payer in the country. While we took adequate measures, we expect the police to provide us with security."

IOC's general manager, operations, Narula, said, "All truck drivers entering the premises have been provided with photo identity cards. And the construction labourers have been given tokens."