The CBI also questioned the family of Bishnoi as he was evading questioning, despite repeated summons issued to him.
Malkan Singh appeared at the Circuit House, Jodhpur but remained uncooperative, that led to his arrest, said CBI sources.
Earlier, Amar Chand, husband of Bhanwari Devi in a written statement to the CBI, had disclosed that Malkan Singh fathered their third child.
Mahipal Maderna, former Rajasthan Minister's wife Leela was also questioned by the CBI in connection with the case.
“We have been a victim of media trial," she said.
Indira Bishnoi, sister of Malkan Singh, another suspect in the case has also been interrogated a number of times and is absconding at present.
Bhanwari Devi, an auxiliary nurse went missing on Sept 1 from Bilara and has been untraceable till now. Bhanwari's husband had alleged that she was abducted at the behest of Maderna before confessing to his part in the plot last week.