An animal cruelty investigation into celebrity dog trainer Cesar Millan, known as the "Dog Whisperer," has ended and no charges will be filed, a spokeswoman with the Los Angeles County District Attorney's Office said on Monday.

The Department of Animal Care and Control in Los Angeles County launched the investigation after a Feb. 26 episode of the Nat Geo WILD TV series "Cesar 911", in which Millan trains a French bulldog-terrier mix called Simon to co-exist with his owner's pot-bellied pigs after having killed two of them.

On the show, Simon is seen chasing the pig and nipping its ear, causing it to bleed.

The investigation by the district attorney was dropped due to "insufficient evidence," said Jane Robison, a spokeswoman for the office.

Millan's attorney, Brian Klein, said his client cooperated fully with the investigation. "His methods are safe and humane," Klein said by phone.

RELATED: ‘Dog whisperer’ Cesar Millan investigated for animal cruelty

A change.org petition signed by more than 13,000 people called Millan's methods inhumane, saying he "used the pig as a bait for the dog all for 'entertainment' purposes." It asked Nat Geo WILD to cancel his show.

Millan, 46, who found fame through his "Dog Whisperer" TV show that has been broadcast worldwide and who has sold millions of books about his training techniques, said he disagreed that he used the pig as bait to provoke the dog. He added that Simon and the pig "became best friends" and the dog was no longer aggressive to toward pigs.

In a follow-up segment, which was aired later in the episode, Simon is seen co-existing peacefully with a group of pigs, a chicken and other animals.

The American Humane Society said it received complaints about the episode, and called the incident "abuse" in a statement.

Nat Geo WILD, a unit of 21st Century Fox, rallied around Millan and said that a clip from the episode that was shared online "caused some concern for viewers who did not see or understand the full context of the encounter."