Kolkata, Apr 12 (IANS): Kolkata witnessed history on Wednesday as a rake of Kolkata Metro conducted a successful trial run through an underwater tunnel under Hooghly river in the route connecting Esplanade in central Kolkata with the iconic Howrah station.

Only senior officials and select engineers of Kolkata Metro were on board during the trial run, the first in the history of the nation.

Describing the event as a historic moment for the city, Kolkata Metro General Manager P. Uday Kumar Reddy said that this is just the beginning and regular underwater trial runs in this route will commence soon.

Reddy, who described the trip as "revolutionary", was part of the first trial run as he travelled from the Mahakaran station to the Howrah Maidan station.

According to Reddy, regular trial runs on this route will be conducted for the next seven months.

"Soon after that, regular services for the general public will commence," he said.

The route stretching from Howrah to Esplanade is approximately 4.8 km long, of which 520 metres will be through the tunnel under Hooghly River. The tunnel is 32 metres under the water surface level.