Police are to investigate reported breaches by nationalist protestors of a Parade Commission ruling during a march in Belfast last night.
During the Orange march, 18 police officers were injured and eleven other people were hurt, including a 14-year-old girl whose arm was broken.
A PSNI spokesman confirmed officers will carry out a full investigation into what happened last night.
The violence erupted after Orangemen and their supporters passed through the mainly nationalist Ardoyne area in north Belfast.
They were attacked with bottles, stones and golf balls as they made their way home from the city centre.
Local residents also clashed with police, who sought to create a corridor between the marchers and nationalist residents. Water canon was used to disperse protesters.