A horse has died during filming of the family film My Friend Flicka, a remake of the classic 1943 movie.
The mustang horse was killed during filming at the Hansen Dam Equestrian Center in California, according to industry paper Hollywood Reporter.
The horse is believed to have broken its neck when it stepped on its own lead rope while running.
Twentieth Century Fox said it had taken "every possible precaution" and was "terribly saddened by the events".
The City of Los Angeles' Department of Animal Services has ruled that the horse's death was an accident.
Production was not shut down and filming resumed on Tuesday.
'High risk'
The American Humane Association, which had four monitors on set, said it was investigating the incident and would be putting further protective measures in place.
"Horses are particularly at high risk when there is intense action, so we're looking at adding another level of supervision and looking at stricter guidelines," said spokeswoman Sara Spaulding.
The organisation claimed another horse on the set had to be put down two weeks ago after it broke its leg. Neither Twentieth Century Fox nor the Department of Animal Services could confirm their claim.
My Friend Flicka is based on the best-selling book by Mary O'Hara, but the remake sees the central Roddy McDowall role replaced by a female character.
It is scheduled for release in February 2006.