Philippine employment officials warned Filipino entertainers in Japan on Thursday against acquiring or using the "Bangkok pill," a popular but illegal diet tablet that has been found to contain harmful ingredients.

Philippine Overseas Employment Administration chief Reynaldo Regalado said in a statement that workers found in possession of the drug face prosecution under Japanese law.

The Bangkok pill, so named because it is imported into the Philippines from Thailand by black market traders, became a craze in Manila about a year ago.

Regalado said he has received reports that some Filipino entertainers in Japan ask friends or relatives to send them Bangkok pills to lose weight. Others obtain the pills through the mail.