Head-on: Police examine the scene of a crash north of Oamaru.

Embattled Timaru financier Allan Hubbard and his wife Jean have been involved in a serious accident north of Oamaru.

They were in a car that collided head on with a four-wheel-drive utility towing a trailer on State Highway 1 at Richmond, at 1pm today.

Allan Hubbard is understood to have life-threatening injuries and was flown by helicopter to Dunedin, while his wife was moderately injured.

Andrew John Earl, 40, from Nelson, was driving the utility. A police spokeswoman said Earl was assessed at Oamaru Hospital and discharged with cuts and abrasions.

Margaret Jane Hubbard, better known as Jean, 82, sustained fracture injuries and was taken to Dunedin Hospital by ambulance.

Allan Hubbard is facing fraud charges after a Serious Fraud Office (SFO) investigation.

The Hubbard's daughter Lesley Limbe said earlier today that she could not comment "because we don't know the full circumstances.

"We want all the family members to be notified first."

Police and emergency services attended, and a crash investigator was called in to examine the scene.

The scene examination has since been completed but the investigation was continuing, police said. The investigation could take weeks to complete.

Oamaru police had spoken to some witnesses but were keen to hear from anyone who saw the crash.

State Highway 1 is closed and a detour is expected to be in place until at least 7pm.

In June, the SFO said it had completed its investigation into the affairs of Aorangi Securities (ASL), a Hubbard-run investment company, Hubbard Management Funds; and ASL directors Allan and Margaret, known as Jean Hubbard.

The SFO laid 50 fraud charges against Allan exactly a year after the Government announced it was placing the Hubbards, seven charitable trusts and ASL under statutory management.