Seven banyan trees were felled by the Salt Lake civic authorities in a night-long drive on Wednesday.

?The trees were damaging sewer lines and some were blocking traffic signals,? said Tapas Chowdhury, executive officer of Bidhannagar Municipality. ?All legal measures were taken before the trees were chopped off.? Civic workers were accompanied by the police during the drive.

This was the second authorised felling in a few months. The earlier one was undertaken for the same reason.

The pockets where trees were chopped off on Wednesday night included Karunamoyee and water tank No. 4.

The sewer lines in the township pass under the boulevards. ?The trees had long roots that had severely damaged the pipes,? said an official. He alleged that the trees were planted in an unplanned way.

The decision to cut the trees was taken by the civic authorities a few years ago. But the plan had to be shelved because of resistance from residents.

Trees on residential plots, too, are a cause of worry for the authorities. Several plots across the township have big trees like coconut, mango and krishnachura.