An oil tanker registered under the flag of the Marshall Islands was suspected to have been involved in an "accidental collision" with a Philippine boat in the South China Sea that killed three fishermen, the Philippine coast guard said Wednesday.

Philippine coast guard spokesperson Armando Balilo said that the incident was under investigation but that coast guard monitoring pointed to the Pacific Anna, registered under the flag of Marshall Islands, as the likely vessel that collided with the fishing boat.

The coast guard said in a statement the Philippine boat "failed to detect" the approaching foreign vessel because of poor weather, resulting in a collision that caused the boat to capsize. Among those who died was the captain.