Murtza Chaudhry, 21, Arbaaz Hussain, 21, Zeeshan Khalid, 20, and Tayyab Siddique, 22, all died when their car hit a tree in Toller Lane, Bradford, in the early hours of August 2, last year.
The BMW the four men were travelling was being followed by an unmarked police car when it crashed into a tree at about 5.30am.
The crash was referred to the Independent Office for Police Conduct (IOPC) and the watchdog has now concluded its findings, which have been passed on to West Yorkshire Police.
The IOPC investigation examined in-car footage and audio transmissions from the unmarked police car; detailed accounts from the officers in both the unmarked car and from other officers who attended the scene; accounts from a number of witnesses in the area, and local CCTV from the scene.
The IOPC say the officers involved have been treated as witnesses throughout the investigation.
Regional director Miranda Biddle said: "Firstly, our thoughts remain with everyone affected by this incident including the families, the emergency services and the wider community. I would particularly like to thank the men’s families and officers involved for their engagement throughout our investigation, which has enabled our investigative team to conclude their work as promptly as possible.
"Our final report is now with West Yorkshire Police for their consideration, as is the proper procedure. The families of the young men who died have received regular updates from us throughout the investigation and we will discuss our report with them soon. The next step is to await the conclusion of any inquest proceedings before we can consider the publication of our findings.”