A National Security Council (NSC) official on Monday said bottles seized from Chinese fishing vessels operating near Ayungin Shoal tested positive for cyanide, raising concerns over threats to marine life, Filipino fishermen, and troops stationed in the area.

Speaking at a press briefing at the Philippine Coast Guard’s West Philippine Sea Transparency Office in San Miguel, Manila, NSC spokesperson Cornelio Valencia said laboratory tests confirmed the presence of the toxic substance in items recovered by the Philippine Navy from Chinese sampans.

“Laboratory analysis conducted by the National Bureau of Investigation’s Forensic and Scientific Research Service has conclusively established that the yellow bottles seized from the sampans contain cyanide,” Valencia said.

The bottles were seized during separate operations in February and October 2025.

Valencia said the use of cyanide poses serious risks to the fragile marine ecosystem, including coral reefs and fish populations, as well as to personnel aboard BRP Sierra Madre stationed at Ayungin Shoal.

He warned that the practice could deprive troops of a vital food source and expose them to contaminated water and fish.

“Such actions, if proven intentional, constitute a blatant violation of Philippine environmental laws and international maritime norms,” he said.

Ayungin Shoal lies within the Philippines’ exclusive economic zone, where the country exercises sovereign rights and jurisdiction.

The NSC has directed the Armed Forces of the Philippines and the Philippine Coast Guard to intensify patrols and monitoring efforts to prevent further environmental damage and protect national interests in the West Philippine Sea.

Philippine Navy spokesperson Rear Admiral Roy Vincent Trinidad said troops recovered at least 10 bottles of suspected cyanide from Chinese boats in multiple incidents in 2025.

He added that personnel also observed a Chinese sampan crew allegedly dumping substances into the water near the shoal last month, with subsequent tests indicating traces of cyanide.

Trinidad said no Filipino troops have tested positive for exposure so far.

Both Valencia and Trinidad alleged that the fishing vessels involved were linked to larger ships associated with Chinese maritime forces.

Valencia said the NSC is preparing a report to be submitted to the Department of Foreign Affairs, which may serve as the basis for a diplomatic protest.