The ruling JD-U in Bihar has demanded a probe into phone call details of RJD chief Lalu Prasad a day after BJP's Deputy Chief Minister Sushil Kumar Modi sought cancellation of the provisional bail granted by Jharkhand High Court to the RJD chief for "violating the bail conditions."JD-U spokesperson Neeraj Kumar said on Thursday that Lalu was on 'bed-rest' on doctors' advice, but he was "busy meeting political leaders." "This is violation of bail granted to the RJD chief," said Kumar, adding Lalu's phone call deatils should be looked into.Senior BJP leader and Deputy Chief Minister Sushil Kumar Modi on Wednesday claimed that the Rashtriya Janata Dal leader was granted bail on medical grounds, and that he was directed to keep off political activities.Lalu, a former Bihar Chief Minister, returned to Patna on Sunday after spending 21 days at a Mumbai hospital, where he underwent a surgery and got treated for a dozen-odd ailments.On May 11, the Jharkhand High Court had granted Lalu six-week provisional bail for medical treatment.On June 29, the High Court extended his provisional bail by another six weeks till August 17 on medical grounds. Yadav's earlier provisional bail was to end on July 3.Lodged in the Birsa Munda jail in Ranchi in Jharkhand since December 23 last year, the RJD leader has so far been convicted in four fodder scam cases, the latest being the Dumka treasury case in which a Special CBI Court sentenced him to 14 years in jail.