KOLKATA, India (AP) — A fire swept through a multistory nursing home in eastern India early Friday, killing an estimated 20 people and trapping many more elderly residents in the smoke-filled building, an official said.

Firefighters smashed the glass walls of AMRI Hospital nursing home in Kolkata and used rope ladders to rescue people trapped on the first and second floor of the building, West Bengal state minister Sirhad Hakeem said.

Television images showed rescuers taking several patients on stretchers to a nearby hospital.

Police said 20 fire engines raced to the scene, and firefighters brought the fire under control after several hours. However, the first three floors are the building were still filled with smoke, and rescuers were searching for others who still may be trapped.

The fire erupted in the building’s basement and heavy smoke soon engulfed the entire building. The cause of the fire was not immediately known.