Traffic has been delayed in two sections of the A470 following two rush-hour collisions.
The road, which links Cardiff to Llandudno, has been closed in both directions between Rhayader and Newbridge-on-Wye.
Emergency services are at the scene, but it is not known what vehicles are involved or the status of the drivers at this time.
Traffic Wales, the Welsh Government’s traffic agency, has told to drivers to avoid the area and find an alternative route at around 4.55pm.
The A road is also closed between Brecon and Merthyr Tydfil at Nantddu.
Dyfed-Powys Police have Tweeted about the incident and also asked motorists to avoid the area if possible at around 4.47pm.
Again, no details about vehicles or passengers have been released at this time.