The Maharashtra Police has prepared sketches of two persons who may have planted explosives in Pune as investigators suspect the involvement of at least three persons in executing the August 1 serial bomb blasts.

"The sketches of two persons who could be bomb planters are ready. It will not be made public but would be given to the policemen involved in the investigations," a police officer said today.

"Initial probe suggest that the there could be atleast three suspects who have planted bombs that exploded within an area of 500 meters," the official added.

On Wednesday, four low intensity explosions took place between 7.37 and 8.15 pm during rush hour in the heart of Pune on Junglee Maharaj Road, crowded with restaurants, shops and the large Sambhaji Park, popular for family outings in the evening.