Experts carry out tests at the explosion site on the Shakespeare Sarani pavement on Thursday. The cause of the blast remained a mystery 48 hours after it occurred. Picture by Sanjoy Chattopadhyaya

A section of the blast tourists on Shakespeare Sarani on Thursday. Picture by Sanjoy Chattopadhyaya

In Buddhadeb Bhattacharjee’s do-it-now capital, firemen need 100 hours to tame a building blaze and policemen remain clueless even 48 hours after an explosion in the heart of the city.

The cause of the “blast” that ripped through a pavement on Shakespeare Sarani at 9.45am on Wednesday remained a mystery, as various agencies — and several “blast tourists” — visited the cordoned-off spot in front of Hindustan Unilever building.

Of the four injured pedestrians, three were discharged from Nightingale Medicare Centre on Thursday. “Pijush Banerjee needs some more time and treatment. Foreign particles will have to be taken out from his eyes,” said a spokesperson for the medical address next to the spot.

Leading the probe pack were experts from the Central Forensic Science Laboratory (CFSL), who arrived at 9.15am to collect samples. “They have been sent for chemical tests and a report will soon be submitted to the police,” said CFSL director Chandranath Bhattacharya.

The debunking of blast theories continued through the day with officials from the CESC and Greater Calcutta Gas Supply Corporation clarifying that their power lines or gas pipes were not responsible for the explosion.

The star visitor of the day, however, was Panchanan Pramanik, a professor in the chemistry department at IIT Kharagpur. “I got a call last night from a senior police officer, who requested me to probe the explosion. I came to Calcutta this morning and went to the site to collect some samples,” he told Metro.

Prima facie, he ruled out a gas leak as the cause. “It will take us at least two days to test the samples in the laboratory and ascertain the cause,” added Pramanik.

The Calcutta Municipal Corporation, meanwhile, has been urged by the police to check whether any leak in the underground sewer lines had caused accumulation of methane gas and triggered the explosion.

The police are also contacting their counterparts in Jalandhar, where such a mysterious explosion had apparently taken place in 2000. Initially, the cops there had no clue about the blast. “We have asked for the details of the case,” said an official.