HAVASUPAI FALLS, Ariz. - Havasupai Falls, a heavily traveled tourist destination at the the bottom of the Grand Canyon, is known for its stunning beauty and crystal-clear, cool waterfalls. About 25,000 people from all over the world visit every year.

It's not easy to get there. People hike the steep terrain -- 10 miles of trails each way -- and many bring with them ice chests, multiple backpacks and groceries.

But there’s a dark secret lurking in that area, one of horrific abuse toward some of the horses and mules that carry visitors’ gear up and down the canyon.

While the animal abuse has been somewhat common knowledge for 20-plus years in Arizona, many tourists from out of state and even out of the United States haven't heard about it. They pay tour companies thousands of dollars to book the permit to get into Havasupai and for a pack horse to carry their belongings without realizing they're supporting the behavior.

Katie Migliavacca and her sister from San Francisco were looking forward to their hike to Havasu Falls last April. However, shortly after their walk into the canyon, she says they witnessed horses with large open wounds on their backs from carrying heavy objects up and down the trail. She said the animal abuse they witnessed ruined what could have been a trip of a lifetime.

"We're not animal rights activists, and I'm not overly sensitive to knowing horses are work animals, but what we saw was horrible," she said. "We saw horses on short leads and tied to posts on the trail, with no shade or water and they couldn't lay down because the lead was too tight. One horse had its body lying on the trail, but his head was still up off the ground."

She took pictures of neglected horses and posted the images on her Facebook page. Within no time she had thousands of people reading her post.

Some people claim to have witnessed horses and mules beaten with chains, kicked in the face and extremely skinny. They, too, began posting the pictures of the animals on her page.

Within a few days, more than 20,000 people shared her post. She hopes her message reaches those tourists who are considering renting a pack horse when they get to Havasupai.

She’s also directing her outrage to the Havasu Tribal members, the FBI and even the White House in formal letters. She says the tribe has not returned her email or her phone calls. The White House responded with a form letter not offering her assistance, but she says she did speak with someone with the U.S. Attorney's office.

As 12 News first reported, that office prosecuted Leland Joe of Havasupi for horse abuse two months ago. It was the first time ever that the U.S. government stepped in to try to stop the pack animal abuse in the Canyon. It is action that is truly welcomed by activists and tourists alike. The Havasupai Tribe owns the land, and many of its 500 residents there own and rent out their pack animals to make their living.

As word spreads, at least one Flagstaff company -- Wildland Trekking -- recently announced on Facebook it will no longer use the horses because of they way they are being treated, something Migliavacca and many others are very happy about.

She wants other companies to stop using the horses, too, and hopes if tourists see abuse while they're in the Canyon they speak up about it.

"If you travel down there, and you see something that is wrong, speak up about it. Because I think so many people have not said anything because they've just assumed that nothing can happen," she said.

Migliavacca is getting support from a group called SAVE (Stop Animal ViolencE) Foundation. It recently launched an aggressive campaign to promote public awareness of the ongoing violence -- from physical abuse and starvation to overworking and withholding of water -- that group members say these pack horses and mules endure. In a recent interview with 12 News, Susan Ash, co-founder of SAVE said, "Havasu Canyon is a death camp for these pack animals and we refuse to pretend otherwise."

The group has already collected nearly 200,000 online signatures from people all over the world requesting the Havasupai tribe improve the pack animals' living conditions.

We reached out to the Havasapi tribe and the individual who took our call hung up the telephone on us. An email to the tribe requesting an interview has gone unanswered.

In the meantime, Migliavacca, Ash and many others are putting pressure on groups like huge companies including REI and National Geographic to stop using the pack animals on their heavily promoted tours into Havasupai.