Guwahati: Numaligarh Refinery Limited on Sunday ordered an inquiry into the major fire which broke out in its Hydro Cracker Unit.

Both the police and NRL authorities have prima facie ruled out the possibility of sabotage as the plant was located in the centre of the refinery and there were several layers of security in the area.

"Prima facie, it appears to be a case of technical fault caused probably by a leakage but the committee will inquire into the details of the accidental fire," a senior NRL official at the refinery said.

A NRL official said that the committee, headed by an officer of the General Manager rank, would inquire into the cause of the fire and also the extent of damage.

The plant has been closed down and it would take at least a month to restore its operations as its equipment and technology is provided by Chevron, a US-based company.

The fire broke out in the HP Fin Fan Cooler Area of the refinery last evening and onsite disaster was immediately declared.

Fire Service from NRL immediately rushed to the site and started fighting the fire with water and foam. Cooling with water was done for the nearby reactors, other equipment and structures and the fire was extinguished by 9 pm.

Representatives from the district administration arrived at the site and also provided necessary assistance, the official added.

The NRL official said that the fire had not spread to the nearby units and could be contained by the refinery's existing disaster mitigation mechanism.

 Meanwhile, assistance from nearby State Fire Service Agencies from Golaghat, Bokakhat, Dergaon and Jorhat was also kept in preparedness and support from other oil companies including Indian Oil Corporation at Guwahati and Digboi, ONGC and Oil India Limited sought under mutual aid scheme.

There was no injury to persons engaged in refinery operation during the fire as well as during the fire fighting exercise, the official said.

ULFA's anti-talk faction claiming responsibility for the fire had said it had carried out the blast with a 'Magnetic Time Device' on the occasion of its Raising Day.

The ULFA claimed that it had used the same device earlier in the Duliajan and Guwahati refineries but these too had been debunked by both police and refinery authorities with inquiries revealing that both were caused by technical defects.