Mumtaz Khan, or Mumtaz Ahmed Maqbool Ahmed Choudhary as he is named in police records, has been arrested before.

Arrested on Thursday for his alleged role in Terrible Tuesday’s serial blasts, Mumtaz was behind bars in 1992, charged with rioting after the demolition of the Babri Masjid. He was acquitted in the case in December 2005 by the Sewri sessions court.

Officers probing the 7/11 case say Mumtaz ‘‘seems to have known about the blasts in advance’’. And that he provided logistical support to the bombers.

The officers also say they have found that Mumtaz had been calling his brother-in-law Kamal Ahmed Ansari every day during the week before the blasts. Kamal has also been arrested in the 7/11 case; he was picked up from Basopatti village in Bihar’s Madhubani district, but is suspected to have visited Mumbai recently. The police suspect he also knows something about the bomb blast in Delhi’s Sarojini Nagar market last year.

‘‘Mumtaz’s conversations were unreasonably long and there was often mention of Kamal’s links across the border especially in Nepal,’’ says an official. ‘‘Mumtaz had a meagre source of income, but spent a lot on making these STD calls from PCOs. Where did the money come from?’’ Kamal, the official adds, underwent arms training in Pakistan and has been on the radar of intelligence officials for some time.

Investigators say Mumtaz led a mysterious life in Mumbai, and are probing where he spent the Fridays he didn’t visit his brothers.

Investigators have recovered Mumtaz’s passport whose validity has expired. Sources said during interrogation

... contd.