The family of a University of Missouri graduate student who was killed when a Megabus slammed into a bridge pillar along a southern Illinois interstate has filed a lawsuit against the bus operator.

On Aug. 2, Aditi Avhad and her parents were aboard the Megabus heading south on Interstate 55 when it crashed into the pillar near Litchfield, south of Springfield. The double-decker bus was headed from Chicago to Kansas City.

Raghunath Avhad and Vaishali Avhad are suing for wrongful death of their 25-year-old daughter, among other allegations. The lawsuit names Megabus USA, LLC., Coach Leasing Inc., Coach USA Inc., and the driver, Preston Taylor, as defendants.

Megabus spokeswoman Amanda Byers says the incident is still under investigation, and the company continues to cooperate with investigators.