From correspondents in Delhi, India, 06:30 PM IST

Thousands of passengers were travelling by trains into and out of Delhi had no idea that a group of engineers was digging a tunnel under the tracks to facilitate another sleek train to run under it. And the work was completed in three days.

The Delhi Metro Rail Corporation (DMRC) Sunday said that it has successfully completed the tunnelling under the rail lines near the Safdarjung Railway Station in south Delhi.

'Delhi Metro has achieved a major engineering feat by successfully completing the construction work without affecting the running of the trains or hindering the functioning of the airport located nearby,' said a DMRC spokesman.

'The tunnel was constructed 12 metres below the railway line to ensure that the tracks were not affected,' the spokesman said adding that trains ply frequently on that route.

Authorities said the general monitoring of the tracks was done for seven days before undertaking the tunneling this month. A group of engineers and surveyors monitored the process round-the-clock.

A German tunnel boring machine, called the Earth Pressure Balancing Machine, completed the task in just three days.

Delhi Metro is the mass transport system of the national capital and carries over 700,000 passengers every day over its network of 68 km. Construction works are on to add another 120 km to its existing network before the 2010 Commonwealth Games.

DMRC said that they had taken prior permission from the commissioner, railway safety, before executing the project. 'A detailed schedule of the movement of trains on the route was also taken from the railway authorities.'

(Staff Writer, © IANS)