Nadia Superintendent of Police Arnab Ghosh said no arrests or detention have so far been made in the case.
Police have obtained CCTV footage from the school which shows that four persons are involved in the incident.
The police said they are conducting extensive searches across the district.
The nun, who is admitted to Ranaghat Hospital, is said to be stable now, hospital authorities said.
West Bengal Governor K N Tripathi hoped that the culprits would soon be arrested.
Appealing to the people to help the police nab those behind the incident, the Governor said the people also have a responsibility towards this end.
The 71-year-old nun was allegedly gangraped by dacoits at Gangnapur in the early hours yesterday after which a CID probe was ordered into the incident.
According to authorities of the local convent school in Ranaghat sub-division, the gang broke into the convent after 12:30 AM and three-four of them raped the nun after gagging her.
The gang also decamped with Rs 12 lakh.
Chief Minister Mamata Banerjee had yesterday ordered a CID probe into the incident and promised "swift" and "strongest action" against the culprits.
She had said that religious politics was being practised in the name of "ghar wapasi" and that religious fanaticism is on the rise.
District Magistrate P B Salim had termed it as a heinous act and said police were on the lookout for the gang members.

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