Nearly 100 dalits in two Bihar villages converted to Christianity last week.
While sources said the conversions were in protest against discrimination by powerful upper caste Hindus, this could not be independently confirmed.
The converts belong to Ganghar and Milki villages under the Ara block in Bhojpur district of Bihar.
District Magistrate Sanjay Kumar said: "Preliminary report suggests that there is some truth in it [reports of conversions] and we have started investigations."
This is the first major conversion of dalits to Christianity in Bihar after the state was bifurcated in 1999 to create Jharkhand.
Vishwa Hindu Parishad and Bajrang Dal leaders have accused Christian missionaries of luring poor villagers with money and promises of employment.
Reports said in both the villages the converts were provided with bicycles, hands lights, daris (carpet) and Bibles. However, there was no independent confirmation of this.
Kumar did not rule out action against those involved in the conversions if it was proved that the exercise was not voluntary.
