Six hunting hounds were hit and killed by a train when they ran on to tracks in the Devon countryside.
A First Great Western train driver reported hitting the dogs near Ivybridge on Saturday.
Organisers of the Dartmoor Hunt, which owned the dogs, said it was a "very distressing and regrettable" incident.
Tom Lyle, joint master, said: "Nothing like this has ever happened to the hunt before and it was very upsetting to all involved."
Network Rail confirmed a driver had reported hitting the dogs at about 12:00 GMT.
A spokesman said: "We were contacted by the police to alert us that a pack of hunting hounds were unaccompanied on the line.
"We then received a call from a train driver to say that he had gone through the area and had noticed the pack of hounds.
"He reported that his train had struck six of them, who died as a result of their injuries."
Joe Duckworth, chief executive of the League Against Cruel Sports, called for the Dartmoor Hunt to be "held accountable" for what happened.
He said: "Surely if the hunt were following a trail, no-one in their right mind would have laid the scent next to a busy line?"