Seven police pickets were set up near the Tolly’s Nullah and a raft was deployed on the canal behind chief minister Mamata Banerjee’s Kalighat home a day after some parateachers tried to reach her house by wading through waistdeep water. They held placards demanding pay parity with regular teachers.

The raft will have disaster management group personnel who will patrol the canal through the day, officers attached with the chief minister’s security said. Police presence has been increased along Alipore central jail in the lanes and bylanes leading to the canal.

From Wednesday, seven police posts were set up along Alipore central jail where personnel were posted on different shifts to ensure that no one would be able to reach the canal without being frisked or giving a satisfactory reason.

Many residents in the neighbouring areas go to the canal for their daily chores, police said. Civic volunteers from the locality will assist the police to verify that the people going to the canal are from the neighbourhood.

The stretch of the canal that flows behind the chief minister’s home is partially marshy and has not been dredged in several years, sources in the Calcutta Municipal Corporation said.

CMC boats sometimes cross the stretch to spray insecticide and larvicide as part of antimosquito drives, said an official of the civic body.

The police top brass is contemplating initiating action against the officers who were on duty and in charge of the security of the chief minister’s home from the Tolly’s Nullah approach, sources in Lalbazar said.

On Tuesday, a group of parateachers had waded through the Nullah and tried to reach the chief minister’s home with demands of pay scale parity with teachers recruited by the government. Mamata was at home at the time.

Calcutta police commissioner Soumen Mitra rushed to the spot and ensured that the agitators were prevented from reaching the chief minister’s residence.

The chief minister’s home on Harish Chatterjee Street is guarded by multiple pickets and heavy radio flying squad vehicles on all sides except one, sources said. The back of her house adjoining the Tolly’s Nullah usually remains unguarded.

The group of men and women who tried to cross the canal on Tuesday had used a bylane adjoining Alipore central jail, apparently unnoticed and unintercepted.