NASHVILLE (AP) - The Rutherford County Sheriff's Office is investigating allegations of Tennessee walking horse abuse at a local stable.

The investigation was prompted by undercover videos the Humane Society of the United States says were taken at ThorSport Farm. They were released to the public on Tuesday.

The new videos show trainers placing what the Humane Society says are caustic substances onto horses' forelegs to irritate them. The illegal training method is known as soring and is used to create the "big lick" gait prized at some horse shows.

A similar video released in 2012 resulted in four people pleading guilty to horse abuse charges and helped spur an ongoing effort in Congress to update the 1970 Horse Protection Act.

A message left at the stable Tuesday morning was not immediately returned.