Several raids to catch fugitive don Gopal Tiwari in Birbhum and North 24-Parganas over the past few days have drawn a blank despite what police sources said were accurate tip-offs that led to the drive.

During some of the raids, police missed Tiwari by a whisker, prompting sleuths to suspect that a section of the force was hand in glove with the don.

Tiwari was allegedly leading a Trinamul gang from which someone shot at a sub-inspector in north Calcutta's Girish Park area shortly after the Calcutta Municipal Corporation elections ended on April 18.

"In some hideouts we found evidence of Tiwari's presence. But he left the places just before we reached," said an officer of the detective department.

"It could be because of involvement of too many policemen in the case. Since Tiwari worked as an informant for a number of officers in the detective department, we can't rule out the possibility of these cops tipping him off about the raids."

Two wings of the detective department are chasing Tiwari in connection with the attack on sub-inspector Jagannath Mandal.

"The two wings are sharing information with each other. At least 30 officers are involved in the probe," the officer said. "Whenever a wing gets a tip-off, it shares it with the other wing before leaving Lalbazar to raid a hideout. The involvement of so many policemen might be one of the reasons for our failure to catch Tiwari so far."

A senior officer not involved in the probe said sharing classified information with so many policemen was not the right thing to do. "This is a high-profile case related to a deliberate attempt on a policeman's life while he was on duty. While dealing with such cases, senior officers should be cautious about sharing information. Ideally, there should be a core team that will handle such information and plan raids," the officer said.

Sources said raids were conducted in Nalhati, Rampurhat, Mayureshwar and Tarapith in Birbhum over the past 10 days.

Among the other places raided was a house in Birati, North 24-Parganas. "The house belongs to Tarak Kotal, who had hurled bombs at the cops during the April 18 attack. We are yet to ascertain whether Tiwari had taken shelter in Kotal's house," the officer said.

Kotal is among the 10 arrested in the case.