For the first time in the history of prisons in the state, the city police have moved in at Presidency jail, Alipore, to put a brake on the growing nexus between jail staff and the undertrials or convicts lodged there.

Four policemen, deployed near the main gate of the jail, frisk the warders while they enter or leave the premises.

The move follows chief minister Buddhadeb Bhattacharjee?s statement in the Assembly, that a host of prisoners ? including Aftab Ansari, alleged mastermind of Khadims owner Parthapratim Roy Burman?s abduction and the attack on American Center ? are in constant touch with their associates outside.

Soon after the chief minister?s statement, inspector-general (prisons) Joydeb Chakraborty met police commissioner Prasun Mukherjee to thrash out a plan for stepping up security in jails across the state.

Sources said Presidency jail was chosen first for the beef-up because several ?high-risk? prisoners, including Ansari, his aide Happy Singh and city gangster Gabbar, are lodged there.

The nexus between the prisoners and jail staff, especially warders, has put the authorities in a spot more than once. Whenever a probe was conducted, it was found that the ?high-risk? prisoners had greased the warders? palms to maintain contact with the outside world.

?Happy had once chalked out a plan with the help of some warders to flee the jail. We, fortunately, came to know about it in time,? said an officer at Lalbazar. ?Besides, a mobile phone was found in Ansari?s cell in 2003. Three weeks ago, it was discovered that Ansari and Gabbar were friends and were planning to help each other out,? he added.

This is the first time policemen have been deployed on a jail?s premises, another officer said. ?Our duty was to look after the areas surrounding the prison?s walls. The arrangement has been made as we have no option but to keep a vigil on the warders, some of whom are used by the prisoners.?

The four policemen posted at the gate have been asked to frisk every warder to ensure he is not passing any contraband to the prisoners. ?We will search them with a hand-held metal detector. The pockets of their shirts and trousers and their bags will be checked thoroughly,? said the officer.

?We have to be extra careful. The prisoners contact their aides outside through SIM cards, cell phones and bits of paper,? he added.

Sources said a section of the warders also supply intoxicants ? ranging from alcohol to heroin ? to the inmates. ?Thanks to the bribes paid by the prisoners, a warder eventually earns several times his salary,? said an officer of Presidency jail.

Vigil outside the jail, too, has been beefed up. The number of policemen outside has been increased.