TAIPEI, Aug. 19 -- Taiwanese actor Kai Ko, also known as Ko Chen-tung, is confirmed on Monday to be detained in Beijing on suspicion of illegal drug use, causing quite a stir in the island's entertainment circles.

Ko and Jaycee Chan, a Hong Kong actor and son of movie star Jacky Chan, were tested positive for marijuana, Beijing police confirmed on its official Weibo account late Monday.

Both of them are being held in custody, and investigation is still under way, it said.

Ko's agent Chai Chih-ping apologized to the public for the actor's setting a bad example in a statement released Monday night.

When Beijing police reached Chai for Ko's case on Monday evening, she "almost broke down at hearing it", Chai said in the statement.

Ko did wrong and should be held responsible, she said. "Being young is not an excuse. Although we cannot fully forgive him, we should also be held accountable for his behavior."

The 23-year-old youngster gained fame for starring in a Taiwanese blockbuster "You Are the Apple of My Eye", which earned him a prize of the Golden Horse for Best New Performer in 2011.

Giddens Ko, writer-director of the film, said on his Weibo that he felt very disappointed and shameful over Kai Ko's doing. "Apart from a punch in the face, I have nothing to say to Ko Chen-teng for the rest of my life," he wrote.