BERLIN (AP) — A man arrested over last week's stabbing attack at a gym in western Germany in which four people were wounded is now also a suspect in a fatal stabbing earlier this month, prosecutors said Thursday.

The 26-year-old Syrian, whom authorities are identifying only as M.D. in line with German privacy rules, was arrested at his apartment in Duisburg on Sunday in connection with the April 18 gym stabbing in the city. He is in custody on suspicion of attempted murder and other offenses.

Investigators initially said that one of the victims in that incident appeared to have been targeted. Earlier this week, however, they said a review of the suspect’s cellphone indicated that “there may have been an Islamist motive.”

North Rhine-Westphalia state's top security official, Herbert Reul, told a committee of the state legislature on Thursday that the suspect hadn't talked in custody about a possible motive.

On Thursday, prosecutors in the nearby city of Duesseldorf said the man was now also a suspect in the stabbing of a 35-year-old man in Duisburg in the early hours of April 9. The victim, who suffered multiple stab wounds, died a few hours after the attack.

In a statement, prosecutors said DNA from the scene and the suspect’s shoes linked him to that attack.

They did not make any new comment on the motive.