A Greymouth family is in ruins following a road crash that claimed the lives of a mother and her teenage son.

Police said the pair, who were travelling with a pre-school boy believed to be 3-years-old, were travelling on Taylorville Rd in Taylorville when their car went over a bank and landed upside down in a creek.

Weather conditions at the time were wet, and the vehicle the trio were in was travelling downhill into a bend, highway patrol sergeant Dave Cross said.

The Greymouth woman, aged 43, and her 15-year-old son - who attended the local high school - died as a result of the crash, which occurred shortly before 11am.


The younger child was transported to Grey Base Hospital, but is now believed to be at Christchurch Hospital.

Grey District mayor Tony Kokshoorn said locals would do their best to support the family.

"He [15-year-old] went to the local high school here.

"It's a small town and everyone feels for them.''

"It's going to be a terrible Christmas for them.''

A serious crash investigation is underway.