People were trapped and injured after a multi-vehicle crash in Rhondda Cynon Taff, emergency services have said.
More than 70 homes lost power after the crash, which involved a bus, affected a power cable.
South Wales Police said “there are casualties” following the collision at Trebanog Road in Porth at about 09:00 BST on Wednesday.
Two people were taken to University Hospital of Wales, Cardiff, and one to Royal Glamorgan Hospital in Pontyclun.
Firefighters are using specialist equipment to extricate people from vehicles.
Western Power is also at the scene dealing with the power outage in the area which appears to have been caused by the incident involving local power cables.
The road is expected to stay shut “for some time” and South Wales Police asked people to avoid the area.