An activist of the outlawed SIMI, Abdul Halim was interrogated on Monday in connection with the serial blasts by the city police which conducted raids overnight and detained several persons for questioning."Those who have been detained by us are being questioned at present. Abdul Halim, a SIMI activist, who was arrested in connection with the blasts, is also being questioned and he is likely to be produced in court for remand," Joint Commissioner of Police (crime branch) Ashish Bhatia, who is heading the probe, said on Monday.Halim was allegedly involved in recruiting people for Jehadi activities, police said.Raids were conducted in different part of Ahmedabad by the police last night and many people were detained for questioning, Bhatia said.The crime branch is also tracking cycles used in the serial blasts held in the city on Saturday. As per police sources, most of the cycles used in the blasts were second-hand ones.The police questioned some of the cycle dealers of the city to find a lead, the sources said.Police were also talking to a person who claimed that he had seen suspected bombers parking cycles in Raipur area in Ahmedabad, they said.Police in Surat sent material from two cars found packed with explosives to a forensic laboratory for tests."We have no found any leads so far about those behind the planting of explosives in Surat city. Several people have been detained for questioning," Surat Police Commissioner R M S Brar said.The 16 blasts in a span of about 70 minutes in Ahmedabad on Saturday left 49 people dead and over 145 injured.Besides Ahmedabad, security has been beefed up in Surat, Vadodara and Rajkot and police are undertaking extensive checking of vehicles. "We are closely monitoring the situation from the Chief Minister's Office," an official said.The army, which had carried out a flag march on Sunday in sensitive areas of Ahmedabad, has been kept on stand-by on Monday, Joint Commissioner of Police H P Singh said. Personnel from paramilitary RAF, CRPF, SRP have been deployed at various places in Ahmedabad and Surat.While primary schools in Ahmedabad and Surat remained closed as a precautionary measure, business establishments, high schools and colleges were open.Abandoned tiffin box found, bomb squad rushesA bomb squad rushed to the Jashodnagar crossroad on the Ahmedabad-Mumbai highway after an abandoned tiffin box was found, police said on Monday. "We have cordoned the area to keep crowd away from the abandoned tiffin before the bomb squad arrives," a police officer said. Whether the abandoned tiffin contains a bomb or not will be determined after the bomb squad arrives, he said. On Sunday, the bomb squad had defused a live bomb in the Amraiwadi area near Hatkeshwar. Another bomb was defused in Surat city.