Philippines says Chinese boats dumped cyanide near West PH Sea outpost

MANILA, Philippines – The Philippines on Monday, April 13, said small wooden boats from Chinese Maritime Militia (CCM) ships dumped cyanide in waters close to the BRP Sierra Madre — a Philippine outpost in Ayungin (Second Thomas) Shoal in the West Philippine Sea — based on samples from at least two confirmed incidents.

“The yellow bottles seized from the sampans contain cyanide, a highly toxic chemical known to cause several damage to human and maritime systems,” said Assistant Director General Cornelio Valencia, Jr. in a joint press conference by the National Task Force for the West Philippine Sea with the Philippine Navy and the National Bureau of Investigation (NBI). 

“The deliberate use of cyanide raises serious concerns…and threaten Navy personnel in LS57 (BRP Sierra Madre). Such actions, if proven intentional, constitute a blatant violation of Philippine laws and international maritime norms and United Nations Convention on the Law of the Sea,” Valencia added.

Valencia said the alleged use of cyanide endangered soldiers stationed on the Sierra Madre several ways — threatening their well being, depleting the fish population in Ayungin Shoal, and threatening the integrity of the reef upon which the Sierra Madre stands.

The amount of cyanide that the NBI tested, said Philippine officials, were more than enough to cause harm on people if ingested. Exposure to cyanide, NBI officials said, could also cause harm on people.

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

Rear Admiral Roy Vincent Trinidad, spokesperson of the Philippine Navy, said no health effects were monitored on soldiers deployed to the BRP Sierra Madre. Still, he told a press conference, “based on the pattern we have uncovered, this is a deliberate attempt not only to destroy the environment but to deprive the men on board [the BRP Sierra Madre] of food and water.”

While water is typically part of the resupply missions to the BRP Sierra Madre, troops stationed on the warship also use desalinated water. Soldiers also rely on fresh fish catch to augment their food supplies.

Trinidad added that even prior to February 2025, Philippine soldiers had monitored Chinese fishing activities in Ayungin Shoal, including suspected use of cyanide and fish nets, which both endanger the marine environment. (READ: Cyanide in Scarborough? PH says it would probe, China says ‘disinfo’)

Trinidad also raised concern that since cyanide is a corrosive chemical, on top of being poisonous, it could also affect the integrity not just of the coral reef but the BRP Sierra Madre itself. Trinidad said the effects on the Sierra Madre have yet to be studied, however.

NBI testing, four documented cases

In at least four documented instances from February 2025 to March 2026, Filipino soldiers who were deployed to the BRP Sierra Madre seized or observed yellow plastic bottles of popular Chinese dishwashing liquid brands from sampans or small wooden boats that were sent out from CMM ships. 

Testing by the NBI’s chemistry division showed that the same bottles seized during two different instances — in February 2025 and October 2025 — tested positive for cyanide. Similar-looking bottles, from a batch seized in July 2025 and monitored in March 2026, were retrieved or documented but not tested.  

CMM are fishing vessels that linger in the West Philippine Sea and, according to Philippine officials, typically act as force multipliers of the China Coast Guard and the People’s Liberation Army Navy in their maritime missions. In flashpoints for Philippine-Chinese tensions in the West Philippine Sea, CMM vessels are used to harass Philippine vessels — both of the government and those belonging to Filipino fisherfolk. 

In the first documented instance of alleged cyanide use in the area surrounding the Sierra Madre, its crew monitored a sampan just one nautical mile away. The wooden ship had been deployed from the CMM ship Qiong Sansja Yu which was some 3.6 nautical miles away from the Philippine warship. BRP Sierra Madre crew were sent to check on the sampan’s activities, which had apparently included diving. 

A boat team later intercepted the sampan and seized four yellow bottles. These same bottles would later test positive for cyanide. 

Months later, on October 24 at around 9:30 pm, the Sierra Madre’s crew observed a blinking white light just some 300 yards from the warship. Boat teams intercepted what turned out to be a sampan, which then tried to flee the area before Filipino soldiers eventually intercepted it and seized four yellow bottles. These same bottles also tested positive for cyanide. 

The BRP Sierra Madre’s crew also seized two yellow bottles believed to have contained cyanide in July 2025, after they saw the CMM ship Qiong Qiong Hai Yu 33858 deploy eight sampans just 2.3 nautical miles away from the Philippine ship. A boat team of Filipino soldiers intercepted one of the sampans and found its personnel to be dive fishing. A search led to the retrieval of the two yellow bottles. 

Most recently, in March 2026, Sierra Madre crew monitored the CMM ship Qiong Qiong Hai Yu 08666 to have deployed five sampans some 3 nautical miles away from the warship. When the sampans sailed closer — just one nautical mile from the Philippine warship — a Filipino team was deployed to intercept the wooden boat. At least one yellow bottle was found in one of the sampans, although Filipino soldiers were unable to seize it. 

Philippine officials noted the presence of dead corals close to the BRP Sierra Madre, along with fishing nets that were used and left behind just some 1.6 nautical miles away from the warship. 

The use of cyanide for fishing is banned in the Philippines, as well as in other Southeast Asian countries. Its use could lead to massive damage on corals that are crucial to support marine life. 

The Philippines also noted a pattern of “research activities by Chinese nationals” inside the shoal. 

The BRP Sierra Madre is a World War II warship that serves as a makeshift Philippine outpost in Ayungin Shoal. It was grounded on purpose in 1999, in response to China building a structure in nearby Panganiban (Mischief) Reef. The structure — which Chinese officials then claimed to be a fisherman’s shelter only — has since turned into a militarized artificial island just around 130 nautical miles away from the Philippines. 

The Sierra Madre, now rusty from decades of being exposed to the elements, has not budged since 1999. It remains in active commission in the Philippine Navy, creating a flashpoint for tensions between Manila and Beijing, which claims almost all of the South China Sea, including areas where the Philippines has sovereign rights and sovereignty claims. 

Ayungin Shoal is a low-tide elevation, which means it cannot be claimed as territory. It is located just over 100 nautical miles away from the Philippines, which means it lies within the Philippine exclusive economic zone, where the country should be able to enjoy exclusive rights to exploit marine resources. 

The 2016 Arbitral Award affirmed both Ayungin’s classification as a low-tide elevation and the Philippines’ EEZ. It also deemed China’s supposed historical claim and 9-dash line, which covers most of the South China Sea, invalid. Beijing, however, does not recognize the award. 

The South China Sea is a critical sealane where up to a fifth of the global trade transits. It’s also a rich resource of fish and possible energy sources. – Rappler.com