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Emergency services were called to a boat ramp on Floyd Bay at Lansvale, in Sydney’s southwest, after the trio were seen in the water in distress shortly after 10am on Saturday.

NSW Police confirmed a 32-year-old woman was pulled from the water a short time later but she could not be revived.

The bodies of a 5-year-old girl and a 7-year-old boy were discovered about 2pm after an extensive search.

Fairfield Police Area Command Acting Superintendent Luke Scott said the woman was found with the help of bystanders and with the support of boats that were commandeered for the search efforts.

“With their assistance we were able to move swiftly through that search op but those two children were unfortunately found deceased,” he said.

“This investigation has moved from a search operation to … (an investigation) into how those people came into the water.

“They were on that pier, the circumstances of how they came off the pier and into the water is what we’re looking into.”

Scott said it’s understood the trio had been at the Shearer Park before they were spotted in the water.

He said that one scenario police were considering was whether the children had fallen into the water and the woman had jumped into rescue them.

However, he stressed the exact circumstances of the tragedy remain “unknown”.

“There’s a number of lines of inquiry we’re looking into … it’s very early in our investigation,” AScott said.

“The three of them were alone, there was nobody else there from their group.”

Scott thanked those members of the public who assisted in the search efforts.

“These are completely tragic circumstances,” he said.

“It’s beyond words for how tragic it will be for anyone who observed this and the family (involved).”

Police believe the current was very strong when the trio fell into the water, with rain, wind, and a “number of environmental factors” affecting the search efforts.

The search involved multiples agencies, including police, Marine Area Command, the Polair helicopter, and SES.

A report will be prepared for the information of the coroner regarding the three deaths.