Wales snow: Carmarthenshire and Pembrokeshire road disruption
Fresh snow has caused more disruption as it spread west across Wales, causing road problems in particular.
In Pembrokeshire, a school bus taking 40 pupils home slid off the road, and some drivers abandoned their cars.
No-one was hurt but the head teacher described the conditions as "probably the worst" he had seen in 25 years.
Forecasters say there is more snow expected in areas of Wales later on Wednesday and Friday, and ice will continue to be a problem.
The school bus was taking pupils home from Ysgol y Preseli in Crymych and was involved in the low speed accident near Maenclochog. The pupils were unhurt and remained on board until a relief bus arrived.
Another school bus and two service buses were said to be stuck on the A487 between Newport and Cardigan, and gritter crews were trying to clear the road.
Vehicles were struggling up Rhos hill on the A478 between Blaenfos and Cardigan.
The council said there were difficult driving conditions in the north and east of the county, and the so-called "mountain road" - the B4329 - closed. Conditions on the A487 coast road between Newport and Eglwyswrw and some drivers are abandoning vehicles around Velindre Farchog.
A spokesperson said the Met Office radar showed snow affecting parts of Pembrokeshire, Ceredigion, and Carmarthenshire is still heavy in places and currently is not showing any signs of weakening as was expected.
Persistent snow moved up into the Swansea, Neath Port Talbot, and Bridgend areas, along with western parts of the Vale of Glamorgan.
First Cymru buses said that all its services in Swansea, Ammanford, Llanelli and Carmarthen were suspended, and all services in Neath would stop at 18:00 GMT.
Swansea City's Capital One Cup semi-final second leg against Chelsea at the Liberty Stadium went ahead as planned, despite the weather problems. The pitch has undersoil hearing and roads around the stadium have been gritted.
Snow blocked one lane of the M4 between Bridgend and Pyle in both directions late on Wednesday afternoon.
Dyfed-Powys Police said main roads in Carmarthenshire were passable but advised motorists only to make essential journeys.
Earlier, three people were taken to hospital after a minibus crash at Drefach in Carmarthenshire, one of a series of crashes in the county.
A motorist was treated at the scene after a crash with a bus in Trimsaran. There were also road crashes as the snow caused problems in Llanelli.
Carmarthenshire council said the situation was "patchy and changing" but its priority was helping keep 1,000km of main roads open. It has already distributed 2,000 tonnes of salt in recent days with gritting teams working 12-hour shifts.
But a councillor, Colin Evans, said they had received reports of some motorists abandoning their vehicles.
"One of the issues is people panicking basically and abandoning their cars," he told BBC Wales.
"How bad that situation is at the moment I'm not sure, but it doesn't help matters when we're trying to clear these primary routes."
Two motorcyclists were taken to hospital after a crash involving two cars in Birchgrove,Swansea, at 09:15 GMT.
Cardiff and the south east had seen the heaviest snowfall overnight, with 10cm (4in) in places.
More than a quarter - 475 schools - closed, mostly in south eastern Wales, but as conditions worsened in west Wales, schools across Carmarthenshire and Pembrokeshire were also affected.
Parents at more than 20 schools in Carmarthenshire were asked to collect their children and eight schools in Pembrokeshire also shut early.
There is a yellow warning in place until 21:00 GMT on Wednesday, with 2-5cm (1-2in) of fresh snow expected, with more on higher ground. Forecasters said ice would be a big problem on Wednesday and Thursday, and more snow is expected in north east Wales and on high ground.
The Met Office said more sleet and snow are expected to spread into mid Wales and the north east.
The lowest temperatures forecast were around freezing or possibly as low as -8C (17F) in places.
Parts of the west and northwest will stay dry.