Philippine anti-drug police said on Thursday they had arrested three people connected to Mexico's feared Sinaloa drug cartel while they were storing narcotics.
The two Filipinos and one Filipino-Chinese were arrested in a raid on Wednesday on a fighting cock farm in Lipa City, 75 kilometres (47 miles) south of Manila, after weeks of intelligence operations by local and US anti-narcotics personnel.
Seized in the raid were 84 kilogrammes (185 pounds) of methamphetamine hydrochloride, popularly known as "ice" or "shabu", as well as two firearms, said police officials.
However the actual members of the Mexican cartel were not there during the raid, said Senior Superintendent Bartolome Tobias, head of a drugs task force.
"We have previously had reports that the Mexicans are here and... this is the first time we have confirmed that indeed, the Mexicans are already here," he told reporters.
Tobias did not say how they knew the Sinaloa cartel was involved
He said a Filipino-American named Gary Torres and two Mexicans known as "Jaime" and "Joey" were being sought in connection with the seized drugs.
It was not clear why the Mexican cartel would have entered the Philippines. The national police chief, Director-General Alan Purisima, said the country's strategic location and the difficulty of guarding the archipelago's maritime borders made it easy to infiltrate.
"It is part of our investigation how the cartel was able to penetrate our country. We are still in the process of determining what is the history behind the arrest of these people," Purisima said.
He said Chinese drug syndicates may be colluding with the Mexicans.
The spokesman of the Philippine Drug Enforcement Agency, Derrick Carreon, said the entry of the Mexican cartel was based on "intelligence reports" but did not elaborate.
The Mexican embassy declined to comment.
The Sinaloa cartel is reputed to be the largest source of illegal drugs to the United States.
Its main leader, Joaquin "El Chapo" Guzman, escaped from a Mexican prison in 2001. He is now America's most wanted drug trafficker, as well as being considered by Forbes as the most powerful criminal on the planet.
More than 77,000 people have been killed in Mexico in connection with organised crime since then-president Felipe Calderon launched a nationwide war against the cartels after taking office in 2006.