German investigators looking into the stabbing and killing of a teenage girl received a breakthrough on Tuesday after the suspected attacker turned himself in to police.

A 15-year-old girl was fatally stabbed in a park in the German town of Viersen, near Düsseldorf on Monday. She was taken to the hospital, but later died of her injuries. Police earlier said the girl was of Romanian descent.

After following false leads on suspects, a 17-year-old boy appeared at a police station in the city of Mönchengladbach along with his lawyer to turn himself in.

A statement from the prosecutor's office and police said the 15-year-old girl and the suspect knew one another. They added that the boy was of Bulgarian descent and lived in Viersen. 

Police said they were still trying to determine the exact motive behind the attack.

False lead

Earlier on Tuesday, police released a 25-year-old man of Turkish descent who had been in custody after it became apparent he wasn't involved in the crime.

Authorities initially suspected the man of being involved in the stabbing after he skipped a police check. He later turned himself in to police on Monday evening, telling them that he fled because he was afraid of getting checked for drugs.

Police cautioned users on social media not to spread false information about the case. They added that detectives were currently investigating all areas, including the victim's social circle.

Police initially reported that they were seeking a man of "North African appearance with glossy black hair" on Monday.

Questions over witness statements

Authorities said faulty witness statements were likely to blame for the false lead on Monday.

The 15-year-old girl's stabbing was observed by a number of people in Viersen's Casinogarten park "who have a dubious quality as witnesses," investigators said.

They added that alcohol may have played a role in the false witness statements.

The Casinogarten park is generally considered by locals to be a well-kept and safe park, according to the German tabloid Bild newspaper.

The area where the victim was found, however, is reportedly frequented by several homeless people who are often seen drinking.

Far-right party quick to react

News of the attack and reports of the falsely-accused suspect's background spread quickly through German media and online.

The far-right Alternative for Germany (AfD) party sarcastically tweeted that it was "another one-off incident," referencing the murder of a 14-year-old girl last week in Wiesbaden.

The case in Wiesbaden sparked a heated debate about Germany's migration policy and asylum system, as it was revealed that the main suspect in the case was an Iraqi man whose asylum application had been rejected back in 2016. The suspect fled Germany with his family, but was captured in northern Iraq.

rs/rg (AP, AFP, dpa)