A person has been flown to hospital with serious burns, and numerous houses and vehicles have been lost in a major bushfire burning in a wide region about 60 kilometres north of Adelaide.

The fire, which started at Pinery, travelled in a south-easterly direction towards Mallala, before a wind change saw it move towards Kapunda, affecting dozens of communities along the way including Wasleys.

An emergency warning for the fire, which is burning north of Gawler near the Sturt Highway, includes Marrabel, Eudunda and Dutton.

The fire has ripped through about 100,000 hectares of land and is believed to have destroyed numerous properties.

Residents have spoken of their panic over the bushfire, with one revealing he had no choice but to leave thousands of animals at a piggery for dead and another describing how his wife was trampled by a horse as she fled.

The Country Fire Service (CFS) said it expected there would be significant property losses and extensive damage from the blaze, which was burning toward Kapunda.

Acting CFS deputy chief officer Brenton Eden told 891 ABC Adelaide the bushfire was travelling in a north-easterly direction and the entire fireground was active.

Sorry, this video has expired Massive fires threaten houses, cars in South Australia

He said current conditions and wind speeds were so severe that ground and air firefighting resources were having little impact.

He said CFS volunteers and other emergency services would work through Wednesday night.

"It's going to be a huge night," he said.

"Many of them are going to be either fatigued or very upset about the results of today so we'll try to bring in strike teams from Victoria to start doing what will be an enormous amount of mopping up and the attention to every single structure that's burnt.

"We anticipate at least five days of work for our interstate resources. This is going to be a massive logistical exercise."

Mr Eden said the CFS knew of many structures that had been destroyed.

"We know there are reports of a significant number of vehicles being burnt out along roads and highways, and of course we have also been reporting that during the day we have also had personnel injured and burnt," he said.

"We're still unable to confirm whether they are CFS firefighters or members of the community."

CFS chief officer Greg Nettleton said he expected the fire would likely take days to control.

He said he had no confirmed information about any fatalities or injuries to firefighters at this time, but there have been reports of serious injuries.

Mr Nettleton said special teams would spend Wednesday evening assessing losses from the fire.

SA Power Networks said the bushfire was affecting electricity supplies across a wide area around Wasleys through to the Barossa Valley.

A bus was burnt out as the bushfire passed through. ( ABC News: Tony Hill )

Weather bureau senior forecaster Vince Rowlands said firefighters were being helped by lower temperatures and higher humidity.

But he said wind changes could cause problems later on Wednesday evening.

"We've got quite a bit of a south-westerly push that's coming across Spencer Gulf up over Gulf St Vincent so we are expecting the winds to probably freshen a touch more during the evening," he said.

Meanwhile, a blaze at Lameroo, in the Murray Mallee near the SA border with Victoria, has been contained.

About 1,700 hectares of land was blackened by that fire, which is believed to have been caused by the spontaneous combustion of a haystack.

Drinking water limited in fire area

Bushfire smoke over the Barossa Valley viewed from Chateau Tanunda. ( Chateau Tanunda )

An SA Water spokesperson confirmed a storage tank in the region has been damaged in the fire.

The spokesperson said the fire had burnt the lining and cover of the Redbanks storage tank, which services towns in the area including Mallala, Dublin, Redbanks, Parham and Lower Light.

They said there was limited water supply in the towns due to the power outage, and it was the main drinking water source serving the region.

"SA Water has been in discussions with SA Health in relation to water quality. While customers may notice an odour and taste, the water is safe to drink," the spokesperson said.

Nuriootpa resident Trevor told 891 ABC Adelaide there was an eerie feeling around town.

"I'm at home on Greenock road in Nuri (Nuriootpa)," he said.

"The situation here is there's no power in Nuri. The traffic is insane because the traffic lights down at the main intersection are not working, there's traffic banked up for probably over a kilometre coming into the town from Greenock."

Meanwhile, the Northern Expressway has reopened at Heaslip Road, but all roads north of Gawler have been closed.

The Goodstart Early Learning Penfield Child Care Centre was evacuated earlier on Wednesday.

Police said all children were safe and could be collected by their parents from Elizabeth Police Station.

Adelaide Metro said a couple of bus routes were having to detour around the bushfire.

Mintaro fire contained

Another fire in the Clare Valley about two hours north of Adelaide has been contained after earlier threatening the town of Mintaro.

A grassfire burned through part of the Clare Valley, approaching the town of Mintaro for a time. ( Supplied: Chelsea Ashmeade, Northern Argus )

About 150 firefighters, aerial bombers, and 20 farm fire units tackled the blaze ahead of a change in wind direction forecast at 3:00pm.

The CFS said the blaze burnt about 200 hectares of grass and stubble and near Quarry Road and Ystalyfera Avenue.

Investigators believe it may have started at a private dump on the side of a road.

Craig Jaeschke, whose property is nearby, said windy conditions pushed the fire through crops quickly.

"I think we're very lucky that we've got quite a slab of lucerne there that's helped stop the fire on the eastern side," he said.

"Under conditions like this everyone has done a terrific job."

Mr Jaeschke said crews would remain on the fire ground for some time.

"Obviously the trees are still smouldering and there's going to be a bit of work to put those out and probably the concern is back where it actually started," he said.

"When the wind change comes, there's not as much protection up in there so hopefully things are ok there before the wind swings around to the south."