Five factory workers died and nearly 20 others fell unconscious after inhaling toxic fumes leaking from a chemical tanker parked near a factory in Gujarat's Surat district early Thursday morning, officials said.

The workers were inside the dyeing factory, located in Sachin industrial area, when the incident took place, Surat Municipal Corporation's in-charge chief fire officer Basant Pareek said.

The fire department received a call around 4.25 am, he said, adding that 25 to 26 workers fell unconscious after inhaling the toxic fumes coming out of the chemical tanker parked on a roadside near the factory.

"They all were rushed to the new civil hospital. At least five workers have so far died in the hospital," the official said.

The fire department later managed to close the tanker's valve to stop the leakage, he said.