An investigation is underway after a serious collision involving a pedestrian and a transport truck southeast of Tillsonburg.

Norfolk County OPP and EMS were called to Highway 3 between Byerlay Side Road and Talbout Street around 2:30 p.m. for the crash.

The OPP's Technical Traffic Collision Investigation Unit was called in to assist in the investigation.

Ontario's Special Investigations Unit (SIU) Tweeted that it would also be "investigating man's injuries after he was struck by truck on hwy 3 near Tillsonburg."

The SIU gets involved when there is death, serious injury or allegations of sexual assault in incidents involving the police.

Highway 3 was expected to remain closed in the area for about eight hours.