According to Montreal law enforcement insiders, someone had called the police to report a fight in the couple's hotel room.
A source told the publication that when the cops arrived, they observed Peters with a bloody nose and Julia Roberts' niece was immediately arrested.
A law enforcement insider told the gossip site that Peters also had a bite mark.
Emma was later released, as Peters did not want to press charges.
A close pal of Emma told TMZ that the pair was hitting each other and the Wild Child star was arrested because he had obvious physical injuries.
The insider denied that Emma bit Peters.