DETROIT – A legally blind social activist from Detroit has gone missing in Peru in a disappearance that has triggered a U.S. State Department and Peruvian police investigation with her family pleading for the public's help in finding her.

Carla Valpeoz, a 35-year-old social worker and trailblazer for the visually impaired, has not been heard from since Wednesday when she was staying at the Pariwana Hostel in Cusco, a city in the Andes about 350 miles southeast of the country's capital of Lima but almost 700 miles by car. She has missed her flights home, her phone has been off for days and investigators are looking into her credit-card activity for clues on her whereabouts, according to family and friends.

Valpeoz, a worldwide traveler and author of "Visionless Adventures," had gone to Peru with a friend for a wedding and had planned to stay two weeks touring various sites.

She spent the first six days of the trip in Lima with her friend, Alicia Steele, 32, of Detroit. The two were supposed to return Saturday to the United States.

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After the wedding, Steele said Valpeoz had planned to go to Machu Picchu, an ancient Incan village abandoned in the 15th century and one of the most popular tourist sites of Peru. Valpeoz went alone on that trip and had plans to meet Steele on Thursday in Lima.

At 11:47 p.m. EST on Dec. 11, Steele received a text message from her friend about her trip to Machu Picchu:

"I can't wait to tell you all about it. It was absolutely worth 100%," the text message read. "I'm coming in on Thursday afternoon so I will send you the details through email once I check in. It would be a wonderful welcoming to have all of you come pick me up."

But Valpeoz never showed up in Lima. She was supposed to arrive at 6:43 p.m. on a flight she had purchased on Orbitz.

Valpeoz is 5-foot-1 with brown hair and brown eyes. She travels with a walking cane when alone. She was last seen traveling with a green backpack.

Steele thought that her friend might have lost her phone, so she decided to meet her at the airport Saturday for their return flight to the U.S.

Valpeoz had traveled the world and been to many countries. She presumed that Valpeoz was OK.

But Steele's friend never showed up for the return flight either. Worried, Steele filed a missing persons report with the police and has stayed in Peru to look.

"We've been searching ever since," Steele told the Free Press in a phone interview Monday from Peru. "The last thing we heard is that a man who works at the entrance of Machu Picchu saw her. She was by herself on the 15th and was going to climb up Machu Picchu. ... She looked well, and she looked good."

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But a lot of confusing information is being relayed, Steele and family said. Valpeoz already had been to Machu Picchu days before.

"This would have been after her flight back to Detroit. She already did that. She spent the entire day there (in Machu Picchu). Why would she have to go back?" said her brother, Carlos Valpeoz of Brooklyn, New York, who has been working diligently to find his sister and has been in contact with some friends she made while traveling in Peru.

According to Carlos Valpeoz, his sister met with a tour group of three Spanish travelers Dec. 11 and a man from Argentina and toured the Machu Picchu site nearly 8,000 feet above sea level together. He has photos of her at the ancient site, and the Ministry of Culture has a record of his sister visiting the site that day.

Carlos Valpeoz said he also learned that his sister went to some hot springs with the travelers she met along the way, had lunch with them and went out dancing at a club.

"She seemed happy and in good spirits. They had a few drinks and danced all night," Carlos Valpeoz said the other travelers told him.

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Carlos Valpeoz said he does not believe that the friends his sister made during her travels know anything about her disappearance. He said they appear genuinely concerned about her and have been working closely with him and authorities in helping trace her steps.

"They seem extremely concerned, really freaked out and very open and willing to discuss anything that I've asked them," Carlos Valpeoz said, noting "they've all reached out to me."

After the night of dancing at the club, his sister sent a message in Spanish to one of her new traveling friends at 10:02 a.m. Dec. 12, according to Carlos Valpeoz.

It read: "Hi. I wanted to tell you I am going on a trip today to check out some places. But I think I'll be back around 1 p.m. and I'll message you to see where you are and maybe we can meet up and see some museums. I hope you got some rest."

That same morning, police have surveillance video of Carla Valpeoz entering a taxi and heading to a street with a bus terminal. It is not known if she got on a bus.

He said the State Department has tracked her to a town called Pisac, about an hour north of Cusco. It's a route people would take if they were headed toward The Sacred Valley, Machu Picchu.

Carlos Valpeoz said that his family is worried, but hopeful, noting that his sister is a savvy traveler who has flown around the world to places, including Egypt, Yemen and Europe. He said media in Peru have reported widely on his sister's disappearance, and he is hoping the American media will pick up on the story in hopes of finding clues that might help bring her home.

"She's a big advocate for Detroit. She's got an incredible heart," he said. "I think she just wants to see the world before she can't anymore. She's got a lot of people rooting for her."

Follow Tresa Baldas on Twitter: @Tbaldas