Additional SP Alex Zarzokima said the arms classified as 'Heckler and Koch' (HK) rifles were believed to have been modified as 'AK series assault rifle'.
Five people, all belonging to Chakma community, were arrested in this connection, he said.
Zarzokima did not rule out the possibility of the arms consignment being smuggled from Myanmar to Bangladesh via Mizoram for the use of Chakma insurgents fighting against the Bangladesh government.
He said that investigations have been launched into the matter.