A massive fire broke out at the South 24 Parganas district administrative office in Kolkata's Alipore area on Wednesday morning, triggering a major firefighting operation and leading to the rescue of a person trapped inside the multi-storey government building.

According to fire officials, the blaze was reported around 9.50 am at the eight-storey building that houses several state government departments. Ten fire tenders were pressed into service to bring the fire under control.

One person stranded on the top floor was safely rescued by firefighters during the operation. While the blaze was largely contained after hours of firefighting, some pockets of fire continued to smoulder, officials said.

Fire officials said the fire originated on the third floor before spreading to the fourth floor, with thick smoke engulfing multiple levels of the building. Flames and dense smoke were seen billowing from the windows, while loud thuds were heard from inside the structure. Parts of air-conditioning units also fell from the building during the incident.

Heavy smoke accumulation, fuelled by paper files and wooden materials stored inside the offices, hampered firefighting efforts. Firefighters initially struggled to access the affected floors through the staircase and used hose pipes to spray water from outside before entering the building.

"The concentration of the fire was on the third and fourth floors," a fire official said.

The exact cause of the fire is yet to be determined. However, officials suspect that a malfunctioning air-conditioner could have triggered the blaze.