M4 crashes investigated by South Wales Police
Police are investigating the cause of two crashes on the M4 near Cardiff involving a coach and six cars which injured 28 people.
The road was closed between junction 33 Capel Llanilltern and junction 34 Miskin after the accidents on Saturday, with traffic queuing for hours.
Many of the injured were pensioners who were on the coach heading from Maesteg to see the Top Hat musical in Cardiff.
Police said they will be speaking to witnesses and looking at CCTV footage.
A woman was airlifted to hospital while 27 others were taken in ambulances following the collisions.
Most were walking wounded but six were more serious. However, none were believed to have life threatening or life changing injuries, police said.
The first accident happened at about 11:50 GMT after the coach collided with four other cars on the eastbound carriageway.
A few minutes later, a vehicle towing another one overturned on the westbound side but no-one was injured.
Eyewitnesses caught up in the disruption said traffic was gridlocked on the M4 and surrounding roads for a number of hours following the crashes.
South Wales Police said its collision investigations unit would be continuing to investigate what had caused the crashes.
A spokeswoman said officers would be speaking to witnesses and viewing any CCTV of the scene.