The bus involved in a crash in the West End on Sunday evening is to be examined as part of the investigation.
Twenty-nine people were injured when the single-decked First Bus mounted an embankment and overturned.
The accident happened at around 7pm on the northbound slip road leading from the Clyde Tunnel onto the A814 Clydeside Expressway.
Twenty-nine people were taken to hospital by ambulance for treatment.
Twelve of those were later released following treatment.
Seventeen people are still being treated in hospital for a variety of injuries - three of whom are classed as serious but stable.
Inspector Darren Faulds is leading the investigation into the cause of the crash.
He said: “After officers arrived at the scene, they spoke to 28 passengers and the driver of the bus.
“Our investigation is continuing today into the cause of the crash.
"The bus involved will be fully examined and officers are gathering and studying CCTV footage from the area to assist with their enquiry.
“At this time, I would urge anyone who may have been on the bus and left prior to arrival of the emergency services, or anyone who witnessed the crash take place to contact the Divisional Road Policing Unit at Helen Street."
He asked people to call using the 101 number, quoting reference number 3617 of 29th April.”