Ipswich Mayor Paul Pisasale has assured owners Lyn and Ray McKay their house will not disappear overnight and engineers are confident of fixing the "sinkhole" which is some six to eight metres in diameter and full of water.
"It will get worse for the next couple of hours. It's an exploratory shaft that goes down about 100 metres and there's no need to panic about a neighbourhood falling in, and we will take all the steps to get Lyn and Ray back in their house," Mr Pisasale told AAP.
Mr Pisasale visited the Coal St home in Basin Pocket on Tuesday where he met with local engineers as well as Lyn and Reg McKay.
The couple has been given temporary accommodation for the evening while engineers wait for the sinkhole to stabilise.
The Nine Network has released aerial footage of the backyard sinkhole caving in as water gushes from side to side.
"It's an exploratory shaft that was put in anywhere between 1903 and 1920," Mr Pisasale said.
"You can see this shaft was full up with rubbish and bottles and whoever did it (filled it), didn't follow very good practices.
"We will take all the steps to get Lyn and Ray back in their house. It's the mines department's responsibility."
He said this is an old part of Ipswich and the mine was about 40 metres from where it had been originally marked on the council's town planning maps.
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What is a sinkhole?
A sinkhole is a hole in the ground that is created by a collapse in the surface layer of the earth.
There are two different types - those that occur suddenly, known as cover-collapse sinkholes, and those that happen over time or cover-subsidence sinkholes.
Cover subsidence sinkholes occur when water dissolves soluble bedrocks such as limestone.
Cover-collapse sinkholes occur if there are gaps below the earth's surface, which can often be man-made such as constructing roads or, in this instance, building an exploratory shaft.
