A Hampshire Police spokeswoman said one lane of the M3's southbound carriageway had reopened but drivers were being advised to avoid the area because of long tailbacks and the motorway was not expected to reopen fully until the early hours.
Sergeant Lyndon Barrett at Whitchurch police said: "Police were called to a coach that left the carriageway on the M3, just north of Fleet Services...the driver had become unwell and lost consciousness...five people were taken to hospital but injuries were not believed to be serious."
A coach that overturned on a motorway was carrying 26 passengers, a Hampshire police spokeswoman said.
She said: "The coach is a Dutch-registered vehicle which was carrying approximately 26 persons on board.
"Five persons have been injured as a result of this incident and they have been taken to hospital where they are currently receiving treatment.
"Arrangements are to be made for the other persons for their onward journey to their destination."
A coach carrying around 40 people has overturned while travelling on a motorway, the police said.
The accident, which happened on the M3 southbound a mile from Fleet services, involved a Dutch coach.
None of the passengers was thought to have been seriously hurt in the crash which happened at about 6pm, a Hampshire police spokeswoman said.
She added: "The carriageway has been closed from junction 4a to 5 whilst the passengers are evacuated and the coach recovered. A diversion is in place along the A30, drivers are advised to avoid the area if possible."