WAKEFIELD: Police in New Hampshire say four on-duty Secret Service agents have been involved in a head-on collision that killed the driver of the other car.

The accident happened at about 7 pm Tuesday in the town of Wakefield.

It wasn't immediately known in what capacity the agents were working, but Democratic presidential candidate Hillary Clinton was campaigning in a town hall meeting Tuesday night in Berlin, north of Wakefield. New Hampshire is one of the early voting states in the primary contests that begin in February.

Police said the agents were passengers in a Ford Taurus heading south on a highway when a northbound Mercury Sable with three people crossed over the center line and collided head-on into the Taurus.

The Sable driver, 45-year-old Bruce Danforth, died at the scene. A Secret Service spokeswoman said the agents suffered serious, but non-life-threatening injuries. They and Danforth's two passengers were taken to hospitals.

Police are investigating.