No arrests been made and officers have appealed for any witnesses to come forward.
A referral has also been made to GMP’s professional standards directorate and the Independent Office for Police Conduct, in line with usual procedures.
Parts of both the M66 and M60 closed overnight following the incident, causing long delays on both motorways.
The M66 reopened just after 11:00 GMT.
A separate three-car crash on the M60 anti-clockwise between Junctions 13 at Worsley in Salford, and Junction 12 for Winton, also caused delays of more than 45 minutes.
National Highways said it had caused nearly seven miles of traffic.
