The fatal incident occurred around 2 a.m. early Sunday morning in the 1200 block of I-35 near Palm Valley Road. Authorities reported that three vehicles were involved in the collision.
Police confirmed that three individuals died at the scene. Their identities have not yet been released pending notification of next of kin.
One individual has been arrested on suspicion of DWI in connection to the crash. The name of the suspect has not been released, and it is not yet clear what role that person played in the collision.
All northbound lanes of I-35 were closed for several hours as emergency crews worked the scene, but were reopened by 7:15 a.m., police said.
The investigation remains ongoing, and authorities are urging anyone with information or who may have witnessed the crash to contact the Round Rock Police Department.