Singer-songwriter Aska, half of the famous pop duo Chage and Aska, was arrested Saturday on suspicion of possessing stimulants, the police said.

Aska, 56, denied the allegations, saying, “I have never used kakuseizai.”

According to the police, Aska, whose real name is Shigeaki Miyazaki, is suspected of having been in possession of a small amount of “kakuseizai” (stimulants) in April.

Also arrested Thursday was Kasumi Tochinai, 37, an acquaintance. The two are suspected of having the drug in Tochinai’s apartment.

The powerful drug’s main ingredient is usually amphetamine or methamphetamine.

Later in the day, police sources said stimulants had been detected in Aska’s urine. They also found what appear to be illegal drugs in his apartment, the sources said.

After debuting in 1979, Chage and Aska produced several hit songs from the 1980s through the 1990s before taking a break in 2009. Their hits, also popular in China and other countries, include “Banri no Kawa,” “Say Yes,”and “Yah Yah Yah.”

Aska also launched a solo career in the midst of the duo’s stardom.

After suspending their activities in 2009, the pair reunited in January last year only to withdraw from the spotlight in October after a weekly magazine reported Aska had allegedly used illegal drugs, which he denied.