Bangladesh Coastguards in separate drives seized six lakh Yaba tablets worth about Tk 30 crore from St Martin's Island in Teknaf of the district yesterday.
They also arrested four people in connection with the incident, said an official of the coastguards.
The arrestees are Babul Miah, Jamir Uddin, Mohammad Idris and Mohammad Jubair.
Coastguards Teknaf station commander Lt Nafiur Rahman said tipped off, they seized 5.5 lakh Yaba from a trawler on the Naf river near Dakkhinpara in the island in the morning.
In another drive, a patrol team recovered 50,000 Yaba from Chheradia in the island and arrested four people in this connection, he said.