The Federal Territories Ministry is investigating whether there was negligence on the part of the contractor of an underpass project where a sinkhole occurred at the Jalan Imbi-Jalan Pudu intersection here yesterday.

Its minister Datuk Seri Tengku Adnan Tengku Mansor said stern action would be taken against the contractor involved if proven that there was negligence.

"The soil instability was caused by a burst Syabas (Syarikat Bekalan Air Selangor) pipe, resulting in the cave-in," he said after presenting the letters of appointment to members of the Federal Territories Non-Muslim Houses of Worship Committee, here, today.

He was asked to comment on the cave-in incident at the underpass project under KL City Hall which left a big, deep hole at the road intersection.

In the 9.30am incident yesterday, part of the 35-metre underground tunnel which is under construction for four vehicle lanes to ease congestion at the Jalan Imbi intersection, collapsed to a depth of five metres following soil movement.

Tengku Adnan said remedial work was going on, including pumping soil and cement to stabilise the affected area, besides checking the Monorail track which was affected by the cave-in incident.

"We hope it will be completed in two weeks," he said.

The minister said the incident was unavoidable, but he reminded contractors carrying out underground works to be extra careful and to study the site condition first in order to prevent any untoward incident.