The chief suspect in the disappearance of Madeleine McCann was reportedly rushed to hospital having suffered two broken ribs in a courthouse holding cell on Monday.
It is understood that convicted paedophile Christian Brückner was taken away under armed guard and placed in handcuffs and leg restraints after the incident.
The injuries are believed to have been suffered while the 43-year-old career criminal was in a holding cell awaiting a court appearance in connection with another offence.
One source at the complex said there was "rioting" on site.
The hearing in the northern German city of Braunschweig had to be delayed while he underwent treatment.
His injuries are not believed to be serious and the hearing eventually got underway two hours late following his return from hospital.
Officials refused to comment on the incident, and it was unclear what had caused Brückner's injuries.
According to an account in Germany's Bild newspaper there was a commotion at the court complex shortly after his arrival.
Cameras got a fleeting glimpse of Brückner as he was driven into the complex just after 11am local time. It was his first public appearance since being identified by German prosecutors as a suspect in the McCann case earlier this year.
Just half an hour later, an ambulance pulled up outside the complex and paramedics rushed out.
"Someone's rioting in there," one of the guards told them, according to Bild.
Brückner was rushed to hospital under police escort and treated under guard. Afterwards he returned to the court complex in handcuffs and leg restraints.
He was in court for a parole hearing. He is currently serving a 21-month sentence for drug offences and will be eligible for parole on January 6.
But even if parole is granted he will remain behind bars. He is also facing a seven-year sentence for rape. Brückner has appealed but will be remanded in custody until his appeal is heard.
It is not the first time that Brückner has allegedly been involved in violence.
A British former girlfriend alleged that he became so angry at her hugging another man in an Algarve bar that he grabbed her and banged her head against a wall. He had to be restrained by four men, she said.
"I didn't talk to the police because I was scared of what he would do if it meant he got arrested," she told the Daily Mirror.
While German prosecutors are treating the disappearance of Madeleine McCann as a murder investigation, Scotland Yard say it is still a missing persons inquiry.
Brückner's lawyers deny that he had any involvement in Madeleine's disappearance in May 2007.
The McCann family have not commented on the case since June, when they denied reports that the German investigators had told them they had proof that their daughter is dead.
Last week, Portuguese press reported that a leaked memo from their Policia Judiciaria said they were "shocked" after being briefed on the German case against, adding there is "no evidence, just speculation".
Portuguese detectives believe the allegations against Brückner are designed to "keep him in prison at all costs", and accused their German counterparts of failing to conduct a serious investigation.
A source close to the family said last night: "This situation doesn't help anything. They just want justice."