The NSW State Emergency Service had to divert crucial resources to answer a flood rescue call that turned out to be a hoax in Sydney overnight.
Commissioner Carlene York said it was the only such incident during the current crisis, labelling it "very disappointing".
The SES received a call purportedly from a person trapped on a roof.
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"It turned out to be a hoax," she said.
"What happens is, because it's to save a life, we target our resources and try to get there to save the person.
"It means we take them away from other areas."
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York also said the SES had carried out two rescues overnight in areas that had previously been ordered evacuated.
She said two people had decided to remain in their homes in Woronora, and ended up in need of saving.
"I know that some people might have moved into the area, some people think that they're experienced in floods, but I think this shows the importance, when we've given an evacuation order, the importance of leaving the area," York said.
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