The Armed Forces of the Philippines is investigating a possible attempt to poison troops stationed at Ayungin Shoal following a reported cyanide-related incident near the BRP Sierra Madre, a Philippine Navy official said Thursday.

Rear Adm. Roy Vincent Trinidad, spokesperson for the West Philippine Sea, said authorities are examining whether cyanide may have been introduced into the water supply system used by troops aboard the grounded vessel.

The BRP Sierra Madre, designated as BRP Sierra Madre (LS-57), serves as a military outpost at Ayungin Shoal in the West Philippine Sea.

Trinidad said the incident stemmed from the confiscation of bottles containing cyanide from Chinese fishermen last year, with findings only recently verified before being disclosed.

“Pinag-aaralan namin kung may attempt na lasunin ang ating mga tauhan, posibleng sa pamamagitan ng paglalagay ng cyanide sa desalinating system,” he said.

China has denied the allegation, calling it fabricated, but Trinidad dismissed the claim as part of what he described as “deceptive messaging.”

“We are not in the process of fabricating information… what we are bringing out to the public is the truth,” he said.

The Navy official also raised concerns over environmental damage in the area, citing extensive coral reef degradation.

The AFP said it is continuing its investigation to determine the circumstances surrounding the incident and any potential threat to personnel stationed in the area.