Two persons - the driver and his helper have been arrested, police said.
Huge quantity of explosive substances were seized from a vehicle in Chitpur area of the city, a senior Kolkata Police officer said on Saturday.
Acting on a tip-off, police officers intercepted a goods vehicle near Tala bridge on the BT Road in the early hours of Saturday and seized 27 gunny bags containing about 1,000 kg of potassium nitrate, the police officer said.
Potassium nitrate is used in making explosives. Two persons - the driver and his helper have been arrested, he said.
"The vehicle was coming from Odisha and was heading towards North 24 Parganas district. We have arrested the driver and the helper of the goods vehicle. We are interrogating the duo and trying to find out more details from them," the officer added.