Amber alert re-issued: Serious concerns for two missing children

There are serious concerns for two Sydney siblings who haven't been seen in almost 48 hours.

Luke and Hayleigh Smith were last seen at a home in Caringbah South on Thursday afternoon, and are thought to be with their mother Nicole Boyle, 36, and a man, Neville Kerslake, 50.

Police believe 12-year-old Hayleigh, 11-year-old Luke, Ms Boyle and Mr Kerslake are travelling in the southern part of NSW in a blue 2005 Ford Falcon with NSW registration DNJ 48E.

There are serious concerns for two Sydney siblings Luke and Hayleigh Smith who have not been seen since Thursday afternoon. Picture: Supplied

In a statement NSW Police said Luke and Hayleigh Smith left a home on Willarong Road, Caringbah South.

Police said they hold serious concerns for their welfare.

There are serious concerns for the siblings who haven't been seen since Thursday afternoon. Picture: NSW Police

Luke Smith is described as being of Caucasian appearance, of thin build, about 105cm tall.

Hayleigh Smith is described as being of Caucasian appearance, of very thin build and about 150cm tall.

It is believed they may be with their mother, Nicole Boyle, 36; and a man, Neville Kerslake, 50. Pictures: NSW Police

Nicole Boyle is described as being of Caucasian appearance, of large build, about 155cm tall with brown eyes and brown hair.

Neville Kerslake is described as being of Caucasian appearance, of medium build, about 175cm tall with brown eyes with grey hair.

Police believe the children are trevelling in a 2005 Ford Falcon with NSW registration DNJ 48E. Picture: NSW Police

Police are asking the public to be on alert and report any sightings of the children, woman, man or vehicle.

Anyone with information is encouraged to call triple-0.|popup=true] immediately.