Mother of sisters who drowned in backyard pool says she screamed for help but it was too late.

Renise Young had just eaten lunch with her five young children yesterday when she noticed that two of her daughters, Taya, 4, and Patricia, 3, had wandered out of the room.

It was Melbourne Cup and as the nation prepared to wind down for the afternoon in anticipation of the big race, this family from Kingston in Logan City had spoken about going for a swim as they’d just cleaned the pool.

The two little girls, the second and third eldest in the family, had a fondness for running up and down the small path that ran across the front of their suburban home so their parents walked outside to bring them back in.

But when they weren’t there they began to panic.

"They thought they went out and walked up the road and they went looking up the road for them, the neighbours were looking,” their grandfather Peter brown told Nine News.

"And it was a last resort going back to the pool and they were at the bottom of the pool."

Ms Young said that her eldest son, Aige, 5, was also looking and when he began screaming she knew.

Somehow, Taya and Patricia had ended up in the water together.

The two sisters had gotten into the fenced area and together had drowned.

Ms Young told The Courier Mail she heard Aige yelling for help.

“All a mother could do when they see their baby like that is just scream at the top of their lungs,” she said.

She dove into the pool and pulled her two daughters from the water.

“I was screaming and grabbing them and making sure their head was above the water and just yelling because there was nothing I could do,” she told The Courier Mail.

Mr Brown told the ABC his daughter and son-in-law were devastated.

"He's cut up something terrible and she's just as bad because she had to dive in the pool to get them out," he said.

"The parents, they done resuscitation and everything on them and the ambulance worked on them as soon as they got here."

Inspector Glenn Allen said ambulance officers responded but were unable to revive them.

"Obviously it's an absolute tragedy that the two of them are now gone."

Inspector Allen said that the parents, Renise and Troy Young will face questions about supervision.

“Imagine just one, let alone two - it must be so awful,” the Inspector said of the tragedy.

He told media that while the pool in the rental property is fully fenced, inspectors are assessing whether the fence was of an appropriate standard.

Nine News reports that police are investigating whether a chair or trampoline could have been used to access the gate.

Ms Young said her daughters were now "at peace".

"We know (they are) at rest, they're at peace, they're not going to go through any pain, they're just sleeping," she said.

Their aunty Tamara Sengstock posted a tribute to the two on Facebook, writing, “R.I.P beautiful girls. Taya and Patricia young, you were both taken so soon.”

She says that she “will miss you so much.”

“I can't believe you beautiful angels were taken so soon and only were 4 and 3yrs old.”

The girl's uncle, William wrote that he already missed the two little girls.

“That's my older sister that lost her babies. My two nieces,” he wrote.

While their other uncle, Zane Sengstock shared the news with his friends on Facebook writing, “R.I.P to my 2 beautiful neices [sic] i will see u both again one day.”