A truck driver has been reported after testing positive for drugs following a multi car crash caused major delays in Adelaide’s north on Tuesday afternoon.

Emergency services were called to a seven vehicle crash on Main North Rd in Evanston South after a semi-trailer rear ended a Toyota sedan causing a chain reaction involving five other vehicles around 3.30pm.

Three people were treated at the scene and taken to the Royal Adelaide Hospital with non-life threatening injuries.

The driver of the truck, a 44-year-old Willaston man, tested positive to methamphetamine.

Officers also found a small quantity of methamphetamine and drug equipment inside the truck.

The man was reported for aggravated drive manner dangerous pending result of a forensic analysis and issued a drug diversion notice.

The truck was defected and towed from the scene.

Heavy Vehicle Enforcement Unit were in attendance.

Southbound traffic on Main North Rd was blocked for hours, with all southbound vehicles diverted via Trinity Drive.

Motorists travelling south on the Gawler Bypass also had to exit at Two Wells Rd.

Anyone who witnessed the incident or has dashcam footage of the collision should contact Crime Stoppers.

Elsewhere, traffic restrictions were put in place after a single car crash on the South Eastern Freeway around 4.08pm.

Restrictions were in place for two outbound lanes just before the Mount Osmond Road bridge.

There are no reports of injuries at this stage.