Two persons died in an alleged explosion while unloading calcium carbide containers at a crowded marketplace in Malda town around 6.30am on Tuesday.

The “explosion”, which the police are probing, triggered a fire that soon engulfed nearby shops and raged on for over 12 hours.

Local sources said the blaze broke out at a calcium carbide storage unit at the Netaji Municipal Market, the largest marketplace in Malda town. The fire raced to adjoining shops, with illegally stored crackers in one of the shops worsening the situation.

Sources said Ganesh Karmakar, 48, and Raju Rishi aka Manglu, 48, suffered severe burns when a container of calcium carbide that they were unloading burst. Firemen later took them to the Malda Medical College and Hospital where doctors pronounced them dead.

Their coworker Azmal Sheikh said: “We were unloading the containers since 4am. Around 6.30am, there was an explosion and the fire broke out.”

Though four fire engines from Malda fire station reached the spot soon, firemen took time to reach Ganesh and Raju inside the calcium carbide storage as the blaze engulfed one shop after another. Crackers burst, making the job of the firemen tougher.

Firemen did bring out Ganesh and Raju from inside the storage, but it was too late for the duo.

The market, across three acres, also has some government buildings, including the income tax office.

A representative of the Malda Merchants’ Chamber of Commerce, whose office is a stone’s throw away from the site, said the market comprises the Netaji Municipal Market, the Netaji Commercial Market, and an area owned by West Bengal Small Industries Development Corporation. The "explosion" occurred in the Commercial Market area.

“There are around 3,000 shops and 50,000 people visit the market every day. If the incident occurred later in the day, the toll would have been higher,” he said.

Traders said 10 shops were fully or partly gutted.

“We are yet to pin down the exact cause of the fire but residents told us of an explosion when carbide containers were being unloaded. Storing inflammable items like carbide and firecrackers should not be allowed in busy markets,” said a fire officer.

Pradeep Kumar Yadav, the district police chief, said they detained some persons and sought forensic tests to ascertain the cause of the fire.

Somnath Saha, the carbide storage unit owner, is absconding.