Philippines says China poisoning with cyanide the waters around BRP Sierra Madre

The Philippines accused China of trying to poison with cyanide the waters around the grounded naval transport, BRP Sierra Madre, in Ayungin Shoal, a senior National Security Council official said.

Filipino fishermen in small boats continue to catch fish while a Chinese Coast Guard vessel looms over in the background. Photo from BFP Sierra Madre Facebook page.

Manuel Mogato | April 14, 2026

MANILA — The Philippines accused China of trying to poison with cyanide the waters around the grounded naval transport, BRP Sierra Madre, in Ayungin Shoal, a senior National Security Council official said.

In a statement, Assistant Director-General Cornelio Valencia said the Philippine Navy recovered bottles of cyanide from several Chinese “sampan” boats operating in Ayungin Shoal last year.

However, laboratory tests confirmed the presence of cyanide in the seized yellow bottles, Valencia said, accusing the Chinese of trying to sabotage the waters in West Philippine Sea.

“We wish to underscore that the use of cyanide in Ayungin Shoal is a form of sabotage that seeks to kill local fish populations, depriving Navy personnel of a vital food source,” Valencia said.

“The operation of Chinese vessels engaging in activities involving hazardous substances in this area is both irresponsible and unacceptable.” (PODCAST: API Podcast Ep2: China’s ICAD tactics)

Valencia said cyanide can damage the reef which can ultimately compromise LS 57’s structural foundations. “If the reef is severely damaged, it not only threatens LS 57’s stability, it also allows Beijing to fabricate an environmental crisis which it can then blame on the Philippines,” he added.

Valencia also said the deliberate use of cyanide raises serious concerns of illegal and destructive practices. “Such actions, if proven intentional, constitute a blatant violation of Philippine environmental laws, international maritime norms, and the obligations of states under the United Nations Convention on the Law of the Sea (UNCLOS),” he added.

The National Security Council said the Ayungin Shoal lies well within the Philippines’ exclusive economic zone, where the country exercises sovereign rights and jurisdiction. (Also read: Chinese warship fires flares as Philippine Coast Guard plane patrols in disputed sea)

The National Security Council has also directed the Armed Forces of the Philippines, the Philippine Coast Guard, and all relevant agencies to heighten maritime domain awareness, strengthen patrols, and take all necessary measures to prevent further environmental harm and safeguard national security interests in the area.

“The Philippines will not tolerate any act—whether by state or non-state actors—that endangers its personnel or the marine environment, violates its sovereign rights, or undermines peace and stability in the West Philippine Sea,” Valencia said.

“The government remains resolute in defending the nation’s territory, protecting its natural resources, and upholding the rule of law.”