Kaitlyn Flanagan and her daughters were last seen in Carrum Downs on September 17.

The 27-year-old mother and her daughters Kassie Bennetti, 8 and Farrah Bennetti, 3 were last seen on Tyas Place about 2.30pm.

Kaitlyn is described as 168 centimetres tall with brown eyes and long light-coloured hair and was last seen wearing a grey cardigan, white T-shirt and grey tracksuit pants.

Kassie has light brown hair, blue eyes and freckles on her face. Farrah has short mid-brown hair with brown eyes.

Police and family members hold concerns for the three due to the amount of time since they have made contact with anyone.

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