Special Investigation Team probing the plot to target the convoy of BJP leader L K Advani during his yatra near Madurai has identified two former hardcore members of banned terror outfit Al-Umma as the masterminds behind the conspiracy.

SIT officials said in Madurai that a manhunt was on to nab them. They said that Fakruddin and Bilal Mallick, close associates of slain terrorist Imam Ali, had hatched the conspiracy as the schedule of Advani's yatra was announced last month.

The investigators suspect that the two were hiding either in Bangalore or Andhra Pradesh and special teams have been sent there.

A powerful pipe bomb was unearthed from under a bridge and defused on October 27 at Alampatti village, about 30 km from Madurai, on the route of Advani's yatra.