LAPLACE, Louisiana (CBSDFW.COM/AP) — A pregnant woman expecting twins and her 7-year-old son were killed in a two-vehicle crash in Louisiana.

Police said 27-year-old Tyandra Lewis was driving a 2005 Toyota Camry traveling eastbound on Interstate 10 when she stopped in the left lane. A 2002 Ford F-350 truck driven by Willy Buchan of Tyler, Texas struck the Camry from behind.

Lewis and her son were fatally injured in the crash. Lewis’ front-seat passenger, 43-year-old Clarence Muse and his 3-year-old son were hospitalized with non-life threatening injuries.

Buchan wasn’t injured. It’s unclear why Lewis stopped in the left lane. It also wasn’t clear if anyone involved in the crash was wearing a seat belt.

The investigation is ongoing.

(© Copyright 2020 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)