An Allenstown man is dead following a rollover crash that threw him from his vehicle on Interstate 93 in Windham Tuesday morning.

Matthew Woo, 51, who was operating a GMC Envoy, was pronounced dead at the scene when state police arrived at the area between exits 2 and 3 on the northbound side around 9:54 a.m., authorities said in a press release.

On scene, troopers found the Envoy on its side and partially in the left lane of the northbound side of the highway, authorities said.

Via investigation, state police said they believe Woo was driving the Envoy on the southbound side when it sideswiped a Mack Truck with a flatbed, driven by Giani Cancellieri, 31, of Brookline.

The Envoy then exited the left side of the road, rolled over through the median, and stopped on the northbound side. Cancellieri was uninjured and stayed at the scene, state police said.

Multiple lanes were closed while authorities investigated; all lanes reopened around 12:40 p.m. Tuesday.

The investigation is ongoing. Anyone who witnessed the crash, or who may have dash cam footage, is asked to contact Trooper Ryan Hajjar at (603) 223-8760 or ryan.j.hajjar@dos.nh.gov.