A crash has closed State Highway 1 near Wilkin St in Ashburton on Thursday.

A crash has closed State Highway 1 near Wilkin St in Ashburton on Thursday.

Two people are in a serious condition, while another is moderately injured in a serious crash that has closed part of State Highway 1 in Ashburton.

Three people were initially trapped in a car when the two-car crash happened on SH1 near Wilkin St, Tinwald, about 11.35am on Thursday.

Two had since been freed, and crews were still working to get the last person out, a Fire and Emergency New Zealand spokesman said.

St John spokeswoman Amy Milne said three ambulances, a first response unit and two helicopters responded.

Three injured people were taken to Ashburton Hospital, but the two people in a serious condition would be airlifted to Christchurch Hospital, she said.

The crash had closed State Highway 1 and traffic was “starting to back up considerably”, Waka Kotahi NZ Transport said in a statement.