Metro Manila (CNN Philippines, May 27) — Joint Philippine and Chinese operatives seized ₱3 billion worth of shabu in Valenzuela City, the Philippine Drug Enforcement Agency (PDEA) said on Saturday.

It was the first time the two countries worked together for an anti-drug operation as part of the protocol on cooperation signed during President Rodrigo Duterte's state visit to China in October 2016.

Authorities on Friday recovered 604 kilos of shabu from two different warehouses in Paso de Blas and Brgy. Ugong in Valenzuela City.

Officials said it was among the biggest hauls for this year.

"We can say that it can be for nationwide distribution," said Wilkins Villanueva, Metro Manila regional director of PDEA.

Investigation began as early as February.

"There were a series of meetings. Pumunta dito counterparts natin (Our counterparts went here) and they started working with us," Villanueva said.

Authorities admit it is difficult to detect illegal shipments now that drug syndicates use high-tech concealment processes.

But "with the help of the Chinese counterpart then we have a better chance of addressing the drug problem," Villanueva said.

Two Taiwanese nationals who were leasing the warehouse remain at large. Authorities mull issuing a hold departure order against them.

The consignee, Fidel Dee, was arrested.

But he denied involvement in the illegal drug trade, saying he is just the caretaker of the warehouse. He said he was made to believe the shipments were machineries.

Dee and the Taiwanese suspects will be charged for violations of Republic Act 9165, or the Dangerous Drugs Act of 2002.