Six racehorses in the US died at the weekend when a fire started in their trailer.

The horses were being driven from Florida to Belmont Park in New York's Long Island on Saturday when the driver noticed smoke coming from the van and saw the horses were distressed through a camera installed in the trailer.

He pulled over and attempted to rescue them with the help of a passenger, but the flames took hold too quickly and all six horses perished.

It is believed a discarded cigarette from a passing vehicle was to blame for the blaze.

The Daily Racing Forum reports that one of the horses belonged to Barry Schwartz, former president of the New York Racing Association and co-founder of the Calvin Klein fashion empire.

The other horses were owned by well-known US trainers.