Serving a lifer in Ajmer Jail, Rajasthan, he was released on December 28 on parole as per Supreme Court orders to visit his family in Mumbai, and was due to return to the prison on Friday (Jan 17).
Referred to as 'Dr. Bomb', Ansari was involved in conspiring and executing over four dozen bomb blasts around the country in the mid-1990s.
On Thursday, his family members complained to the Agripada Police Station that he had gone to offer 'namaz' at 5 a.m. and then went 'missing', his phone switched off and no trace anywhere.
The Mumbai Police have alerted the Maharashtra ATS and others who have launched a massive manhunt to trace and arrest Ansari.
A medico by profession who served with the BrihanMumbai Municipal Corporation at one point of time, Ansari had undergone terror and explosives training in Pakistan in the early 1990s.
He was finally convicted for the Jaipur serial blasts, Ajmer blast and Malegaon blast case and awarded a life sentence in jail.
Besides, Ansari was reportedly involved in several other blasts in Pune, Mumbai, Hyderabad and other places ostensibly as vendetta for the felling of the Babri Mosque in Ayodhya in 1992.
Influenced by a terror mastermind Abdul Karim Tunda, Ansari had developed expertise in timer devices and TNT bombs, besides creating terror modules for IM, HuJI, SIMI, indoctrinating more to their cause, etc.
( With inputs from IANS )