POLICE have launched an internal investigation after an 18-year-old man was injured during his arrest in Thornlie over the weekend.
The man was being sought for questioning over a complaint of suspicious activity in the area.
Police found the man on Sunday afternoon and a scuffle ensued, with one police officer injured.
The man fled the scene an was arrested a short time later on Wilfred Road after colliding with a police vehicle.
He was taken to Fiona Stanley Hospital for treatment to injuries.
The actions of police in relation to the arrest are now the subject of an internal investigation.
Investigations are continuing into the earlier report of suspicious activity in Thornlie.
Witnesses to the incident are asked to contact Crime Stoppers on 1800 333 000 or make a report online at www.crimestopperswa.com.au.