Three of the four teenagers who were injured in an explosion in Bhangar on Tuesday remained critical on Wednesday.

One of them is battling nearly 95% burn injuries, while the other two have suffered 55% and 15% burns, respectively.

Police said the barrel blew up after the chemical came in contact with fire from a glowing object. It was unclear how the chemical came into contact with fire.

The barrel containing the chemical intended for mixing with bitumen for road construction in Khargachi was stored along the roadside. Following the explosion, the liquid splashed out and struck four teenagers, resulting in burn injuries. One of the teenagers received treatment and was discharged from a local hospital, while the other three were transferred to MR Bangur Hospital.

The explosion underscored the dangers associated with road construction sites, where flammable chemicals are often stored carelessly and without adequate protection. Repairs are often carried out without sufficiently securing the materials involved.

Doctors at the MR Bangur Hospital said the health condition of the three teenagers continued to remain critical. “They are under observation round the clock, and the next two days remain very crucial for them,” said an official of the hospital.

Officers of Kolkata Police’s Bhangar division said several chemical barrels and bitumen tins were stacked by the roadside for the repair of a 7km-long road between Ghatakpur and Chutkir More in Bhangar.

The work was held up for the last two days after the mixing unit developed a snag, they added.

“There is a school adjacent to the explosion site. The injured teens were close to the barrel when it exploded,” a senior police officer said.

“A forensic team has visited the site. We are waiting for the findings,” he said.

The explosion led to a fire that also left branches of a tree partly charred. The wall of a nearby building was covered with black soot. A section of residents said the barrels containing a chemical and tins of bitumen have been lying on the roadside for almost a week.

“One of the chemical barrels had started to leak. It somehow caught fire, leading to the explosion on Tuesday,” said a local youth, who had rushed to the spot after the explosion.

Eyewitnesses told police officers that one of the injured teenagers had jumped into a nearby pond after suffering burns.

“We have collected information about the contractor who had taken up the job of repairing the road. He has been summoned for questioning,” the officer said.