Five people are in hospital with two in a critical condition after a bus and ten other vehicles were involved in a serious crash in Rhondda Cynon Taf.
A number of homes have also lost power after a line was damaged as a result of the incident, which occured on Trebanog Road in Porth at around 9am.
Two people have been taken to University Hospital of Wales in Cardiff, and three others have been transported to Royal Glamorgan Hospital in Pontyclun.
Three of those injured, including the coach, sustained non-life threatening, believed to be minor injuries.
Eight cars, one light good vehicles, one van and a bus were all involved in the collision.
Three people who were trapped inside vehicles were freed by the fire service. Another two people managed to free themselves.
Five crews from South Wales Fire and Rescue attended the scene but have since left.
The Welsh Ambulance Service sent three rapid response vehicles, six ambulances and four vehicles from its hazardous area response team to the scene.
People are being urged to avoid the area until further notice as the road is currently closed and is likely to remain closed for some time.
Western Power remains at the scene while it deals with the power outage in the area.
Officers are asking anyone who witnessed what happened to contact them.
A resident who witnessed the incident said: "It looks really bad, there are around five police cars here, ambulances and a fire engine."There is a bus further down the road too. All the power has gone off in the houses around here."