A huge abattoir blaze south-east of Adelaide that caused part of the building to collapse is still burning and dozens of firefighters remain there.

They have said the fire at the Thomas Foods Murray Bridge abattoir has left a damage bill in the millions of dollars.

It broke out at 7:00pm yesterday and about 100 firefighters responded.

At one stage about 100 firefighters were trying to put the fire out. ( Audience submitted )

Five fire trucks were still there this morning and while the fire is contained, it was still burning inside the building.

A caller to ABC Radio Adelaide named Brett said a "slightly sickly, sweet" smell was starting to grip the town.

"A burning rubber sort of smell... yeah, it wasn't real nice," he said.

"[The smoke was] quite thick, almost like a fog driving through it."

The abattoir processes a thousand head of cattle a day. ( ABC Radio Adelaide )

Senior Constable Rebecca Stokes said fire investigators would be sent to the abattoir once it is safe for them.

"Once that fire has been completely extinguished we will be able to send in our fire cause investigators," she said.

"It's not safe for them to enter at this stage."

A massive column of smoke spread from the fire last night. ( Twitter: T-J )

Thomas Foods said employees who were on site "were safely and promptly evacuated" and the Metropolitan Fire Service (MFS) said management managed to move livestock to a safer area.

The MFS's Roy Thompson said firefighters were courageous and quick to cut the fire off.

"Imagine a massive factory about 100 metres by 80 metres about four storeys high," he said.

"An absolute rabbit warren of conveyor belts where all the meats are processed. The crews were fantastic … moving inside the building."

The local mayor, Brenton Lewis, has described the factory as Murray Bridge's largest employer, with a local workforce of about 1,400.

He said the plant is one of the nation's largest privately owned abattoirs and a major exporter of lamb.

Firefighters were still at the scene over 12 hours after the fire broke out. ( ABC Radio Adelaide )

"My understanding from the briefing [by Thomas Foods] is that the fire has not devastated the entire plant, which is of course what we wanted to hear," he said.

"It is too early to for me to accurately give you an assessment other than the company is at this moment taking advice from emergency services."

Residents are being advised to stay indoors to avoid the smoke. ( Twitter: T-J )

Local State MP Adrian Pederick said the abattoir processed a thousand head of cattle a day and 11,000 sheep per day and therefore the fire would cause "short-to medium-term pain" in the meat-processing industry.

"I'm hopeful the slaughter floors are still intact. There's talk that the fire was in the boning room," he said.

"This is a company that turns over well over a billion dollars a year. Thomas Foods will be doing everything in their power to make sure everyone keeps their jobs.

"They do have to assess what exactly has gone on in there."