Two Mumbai men, Arshi Qureshi and Rizwan Khan, who were recently arrested for their alleged involvement in recruiting youths for terror outfit Islamic State, facilitated the conversion, sources said.
Several marriage certificates and other documents were seized from Rizwan Khan by the Anti-Terrorism Squad (ATS).
According to sources, Khan would also conduct 'Nikah' (marriage) for couples among the converts. After documentation, he would send vouchers with individual expenses to get them reimbursed.
The agency have initiated a probe to check if the conversions were forceful.
In a report filed before the District and Sessions Court seeking police custody of Qureshi and Rizvan Khan, who was also held from Mumbai last week, police claimed both had facilitated recruitment of Merin alias Mariam, who is missing along with her husband Bestin Vincent alias Yahia from the state, to ISIS.
Both Qureshi and Rizvan Khan were sent to 14 day police custody by the court.
"Aarshi Qureshi has been working as the Guest Relations Officer of Mumbai-based Islamic Research Foundation. A thorough probe is required to find out whether this organisation has any role in the case," the report said.
Kerala police had traced Qureshi to Mumbai following a complaint lodged in Kochi by the brother of a young woman, who is suspected to have joined ISIS along with her husband.
Ebin Jacob (25), brother of Merin who is missing along with her husband Bestin Vincent from Kerala, had told police in Kochi that there was an attempt to forcibly convert him to Islam and make him join ISIS, and that Bestin and Qureshi were behind it.
Based on this, Kerala Police slapped charges under Section 13 of the Unlawful Activities (Prevention) Act on the duo and booked them under sections of the IPC.
Both Qureshi and Rizwan Khan, arrested by Kerala Police and aided by Maharashtra Police in two separate operations last week, were brought here yesterday by air under tight security for questioning.
While Qureshi was arrested on July 21, Khan was picked up from his residence at Kalyan in Thane district on Friday night.
(With input from PTI)