The flooding of Park Street Metro station and the tunnel between Park Street and Esplanade stations on May 28 was caused by leaks in the sewer line of the Kolkata Municipal Corporation (KMC), Metro Railway said in a formal statement on Thursday.

This statement contradicted the version of KMC officials, who had said on Wednesday that water seeped through the diaphragm wall of the station and there was no leak in the sewer line. A senior Metro official had on Wednesday told this newspaper that the water ingress was because of the damaged sewer line, which is contiguous with the Metro premises.

Overnight rain caused by Cyclone Remal flooded Park Street station and the tunnel leading to Esplanade station, crippling the transport lifeline of Calcutta for hours on May 28. Engineers of the KMC and Metro Railway conducted a joint inspection of the stretch on June 10.

“During this joint inspection by the officials... it has been found that the century-old brick sewer of Kolkata Municipal Corporation has been silted and has pores and holes in the manhole wall. Three holes have also been found in the wall of the brick sewer through which water entered into the station area on May 27,” the Metro statement on Thursday said.

“Metro Railway and KMC authorities are working in tandem to stop recurrence of such incidents in the future. Engineers of KMC have assured to desilt the brick sewer in order to clear it so that water can pass through it smoothly and repair the wall. Metro Railway has extended helping hands to close the pores/holes of brick sewer of KMC, if required. After repairing these holes, plastering will be done in order to bring it back to normal condition,” said the statement issued by the Metro spokesperson.

“However, to arrest the seepage from the tunnel wall, Metro Railway has started grouting at locations where visible porous concrete is found in the diaphragm wall,” it said.

Grouting is a process to fill gaps and repair cracks.

Tarak Singh, the mayoral council member who heads the KMC’s drainage department, contested Metro’s version.

“This is not true. There is no leak in our sewer line. But we don’t want any controversy. Metro Railway is the pride of our city. If Metro seeks any help, we will extend it,” said Singh.