The mother of two young boys who drowned in Townsville's Ross River has been charged with manslaughter, after police allege it was a "preventable tragedy".

Key points: The bodies of Townsville brothers, 3 and 5, were found submerged within metres of each other on February 26

The bodies of Townsville brothers, 3 and 5, were found submerged within metres of each other on February 26 They had gone missing about 12 hours before

They had gone missing about 12 hours before Their mother is expected to face court on Saturday on manslaughter and drug charges

WARNING: Aboriginal and Torres Strait Islander readers are advised that the following story contains images of people who have died.

Jhulio Sariago, 3, and Barak Austral, 5, went missing late in the afternoon of February 25 and an amber alert was issued six hours later.

Their bodies were pulled from the river the next morning after a desperate community search involving 100 people and a helicopter.

Their mother, 47, was taken into custody on Friday morning and was charged that afternoon with two counts of manslaughter.

She was also charged with drug possession and trafficking, supplying drugs to a minor, permitting a place to be used in the commission of a drug offence and unlicensed driving.

The bodies were found in the Ross River after hours of searching by police and volunteers. ( ABC News: Sally Rafferty )

The supplying drugs to a minor charge was not related to the drowned boys.

Detective Senior Sergeant David Miles said police will allege the boys' deaths were a "preventable tragedy".

"This is something that should have never happened," he said.

"She's been solely responsible for the failure, as we are going to allege, in relation to these two young boys.

The bodies of the brothers were flown to the Northern Territory for burial. ( Supplied: Queensland Police Service )

"This is an investigation that revolves around the care of these young boys and what led to their tragic passing.

"This is a catastrophic result for this family and it is a preventable tragedy."

Senior Sergeant Miles said it had been an "arduous" five-week investigation.

"We [police] go about our task for the purpose of, in this instance, providing a voice for two young boys who are sadly no longer with us," he said.

"We have preferred the charges of manslaughter — they are perhaps the highest standard that can be preferred."

CCTV footage showed the two boys walking away from their home. ( Supplied: Queensland Police Service )

At the time of the deaths, Senior Sergeant Miles said the boys were found in the water within metres of each other.

"They were in a small cutaway area in the river, from recent flood events it's quite deep, and quite a deep bank, and there's some vegetation there," he said.

The boys' bodies were returned to the Northern Territory where they have ancestral and cultural ties.

They were buried together in one small coffin in Darwin after a funeral service at the city's Catholic cathedral.

Their mother is expected to appear before the Townsville Magistrates Court on Saturday.