Even as the Indian Space Research Organisation (ISRO) officials maintained that yesterday’s explosion would not affect the ongoing research activity at Sriharikota’s Satish Dhawan Space Centre (SDSC), questions are being raised about the adequacy of safety measures at the centre.Declining to quantify the loss in terms of rupees, ISRO Chairman G. Madhavan Nair said today after visiting the blast site that the probe committee would submit a preliminary report in a week and the final one within six weeks.Sources at the SDSC said that the officials may have failed to take enough safety precautions in the Solid Propellant Booster Plant (SPROB) building (No 117) where six persons were killed and three others injured in the blast. Engaging casual labour in units like SPROB and absence of safety officers during critical operations might have resulted in the mishap.A few employees, on condition of anonymity, said that the operations in SPROB are highly sensitive as it carries out ‘‘a highly dangerous stage of mixing the propellant and curing it’’. Even a small spark would lead to ignition of booster motors causing explosion.