Parts of the A48 have reopened following a three-vehicle crash between Cross Hands and the junction for the National Botanic Gardens.
Police said it involved two police vehicles on their way to an immediate call.
Police said the third vehicle was not damaged and the two members of the public did not suffer any injuries.
But four officers have minor injuries.
The collision happened at 1:20 this morning.
The east bound route has reopened but west bound between Llanddarog and Crosshands Roundabout remains closed. Police are expecting the full route to reopen at 2pm.
There is a diversion via the A467 through Tumble and the B4310 via Llanddarog, Porthyrhyd and Cwn and Vice Versa.
Dyfed-Powys Police are asking drivers are asked to find an alternative route.