Five more people have been arrested by detectives investigating the events leading up to the crash on the A66 that killed seven people, including two police officers.
Cleveland police made the announcement after 12 people were arrested on Monday.
PC Matthew Blades, 37, and PC Tom Clough, 38, were killed when a Volkswagen Passat, which had been pursued by police, was driven the wrong way along a dual carriageway near Middlesbrough and hit their marked armed response vehicle.
The five people travelling in the Volkswagen, Cole Robert Worthy, 17, Theo Rae, 17, Makai Saddington, 18, and 23-year-olds Michael Robert Cahill and Jacob Matusiak, were pronounced dead at the scene at South Bank, early on Saturday.