MANILA, Philippines -- The chief of the Philippine Drug Enforcement Agency on Saturday issued a stern warning of possible arrests to showbiz personalities who continue ignoring his calls for them to stop using illegal drugs after the matter came to the fore in the wake of a recent sex video scandal.

Without naming names, PDEA Director General Dionisio Santiago said his operatives will continue investigating reports of celebrity involvement in drugs even while some stars they would like to question have been ignoring the agency.

?They think they're more popular than the PDEA. And we have a problem if that's their attitude. Nobody would come to me if that's the attitude? we won't be able to talk to anyone,? Santiago said at a news conference.

?So we'll find a way for them to talk to us. We will continue to operate and we are warning them. We know them, we will hit them when we can,? said Santiago.

The PDEA has long said it has been investigating the distribution of illegal drugs within celebrity circles.

The agency has received information that some showbiz personalities were using illegal stimulants ?primarily to pump up energy and stamina to meet the rigors of their work,? an earlier PDEA statement read.

This effort received attention recently when the PDEA looked into allegations that actress Katrina Halili had enticed cosmetic doctor Hayden Kho into using drugs.

Kho's mother Irene made such allegations in a television interview after a video of Kho and Halili having sex surfaced online and on DVDs on sidewalk stalls. Halili has denied the charges and has haled the younger Kho to court for taping their lovemaking without her knowledge.

Both celebrities tested negative for drug use, but PDEA officials conceded the urine tests could trace only recent drug consumption.

?Tintawanan kami ng iba eh they think we're joking. But we will be watching. Next time, mababawasan na mapapanood 'nyo dahil ide-detain namin yan,? said Santiago.

Santiago recently sent a letter to the Actors' Guild of the Philippines asking the organization to ?initiate measures that would prevent the proliferation of illegal drugs in the entertainment industry.?

The letter, sent to guild president Philip Salvador, also volunteered PDEA's ?technical assistance? in such an undertaking.

Santiago said he has yet to receive a reply from the actor and would make ?a personal follow-up? and maybe even invite the action star to his office for a dialogue.