A court in southern Thailand has issued arrest warrants for four military officers in connection with the trafficking of ethnic Rohingya migrants.

Police Lt. Gen. Paveen Pongsirin said Monday warrants have now been issued for 153 people, 90 of whom have turned themselves in or been detained.

The authorities began their crackdown in May after discovering more than 100 bodies buried in squalid camps built to hide the migrants along the Malaysian border. Rohingya migrants continue to flee Myanmar to escape discrimination and seek better economic opportunities.

The new suspects are a colonel and two captains in the army who belong to the Internal Security Operations Command, a counterinsurgency agency, and a navy commander. An army major general was arrested in June for alleged involvement in human trafficking.