The coins, specifics of which are not immediately available, were found last night by labourers, they said.
Local people also started digging following the discovery and found unspecified number of coins, police said.
The police surrounded the area, in the outskirts of Malda town and near Kalindi river, this morning and seized some of the coins from local people.
Historian Kamal Basak said there had been a town in ancient times in the area from where the coins were found.