India, Nov. 18 -- Investigators have detected "trace" amounts of ammonium nitrate on the bed, floor, window and even on recovered hair strands inside the Al-Falah University hostel room where alleged suicide bomber Umar un-Nabi worked and stayed, officials said on Monday.

The findings, based on a forensic sweep of Room No 13, suggest that Umar may have stored explosive materials in the room - either as stock, in test batches, or while assembling components of the bomb later used in the November 10 Red Fort blast, a senior police officer said. Umar died in the explosion after he allegedly detonated an improvised device inside a Hyundai i20, killing at least 11 others.

Police believe the module had prepared for "serial blasts" based on th...