Perth County OPP are investigating a crash involving a school bus and gravel truck near Stratford. On Wednesday morning around 7:40 a.m., emergency services responded to the incident at the intersection of Line 39 and Road 125. The bus driver sustained serious injuries, and an adult passenger sustained life-threatening injuries. Police confirmed there were no students on board at the time. The driver of the gravel truck sustained minor injuries. Line 39 is closed between Road 130 and Road 122. Road 125 is also closed between Line 42 and Line 36. These closures are expected to stay in place for several hours as the investigation continues. Drivers are asked to avoid the area. If you witnessed the crash or have video surveillance or dash cam footage of it, you are asked to contact Perth County OPP at 1-888-310-1122. Anonymous tips can also be sent to Crime Stoppers at 1-800-222-8477.