Six people died in a nine-vehicle wreck on Interstate 75 in Tennessee Thursday, police said.

Chattanooga Police Department spokesman Kyle Miller said the accident happened around 7:10 p.m. on I-75 northbound near Ooltewah.

Miller said investigators were working overnight to determine the cause of the crash.

Police believe more than 15 people were involved in the accident. However, the exact number is still being determined because multiple groups were taken to local hospitals.

The identities of the victims have not been released.

Northbound lanes of I-75 were shut down after the accident and traffic was redirected. Police expect the lanes to be closed into the early morning hours.

The Associated Press contributed to this report