Magdeburg, Germany  - The motives for a recent attack on the drummer of German pop band Tokio Hotel were still unclear on Wednesday, according to police officials.

Drummer Gustav Schaefer was hit on the head with a beer glass in a disco in his home town of Magdeburg late Friday night.

The 20-year old received cuts which needed more than 30 stitches.

Police are investigating on charges of dangerous bodily harm, and plan to question three witnesses as well as Schaefer himself this week.

"Gustav has always tried, despite his Tokio Hotel career, to maintain as much of his "normal" life as possible," manager David Jost said, adding that the drummer didn't use bodyguards when he went out privately.

Jost said it was unclear whether Schaefer was hit by a beer bottle or a beer glass. There is also confusion over the number of attackers. The police spoke of one person, while Jost said two were involved.

Tokio Hotel's manager said the band members have been followed and threatened by stalkers for several years. (dpa)