Crime branch will investigate the allegations against five priests of Malankara Orthodox Church in Kottayam district of Kerala.
The matter was earlier investigated by the church itself.
The Director-General of Police handed over the letter of former chief minister VS Achuthanandan, in which he asked the crime branch to probe the matter.
One member of the church alleged that five priests blackmailed and sexually abused his wife, using her confession secrets. The man also said that his wife was facing the abuse even before they were married.
The issue came into light after an audio clip was recovered by the husband of the victim.
Meanwhile, a church spokesperson said that "the victim was subjected to sexual abuse by blackmailing her with her confessional secrets."
The Malankara Orthodox Church suspended five priests after the complaint.