Nancy Ng on bridge

SEE IT: Video Shows Missing California Woman Nancy Ng in Kayak, Waving at Camera Before Disappearance

The family of a missing California woman is questioning officials who claimed she may have drowned, as a video surfaces showing her paddling in water on a kayak.

As CrimeOnline previously reported, 29-year-old Los Angeles resident Nancy Ng vanished on October 19 at a yoga retreat by Lake Atitlán in Guatemala. She flew to Guatemala on October 14, and a few days into the vacation, the retreat organizer contacted Nancy’s father to say she could not be found.

The Guatemalan prosecutor’s office indicated that a witness said Nancy was spotted in the water on a kayak and decided to jump in the water for a swim. Officials told ABC News that they found Nancy’s empty kayak in the water and that she likely drowned, but family members are concerned about such a simple explanation.

For unknown reasons, the witness didn’t report the incident until 24 hours later, and family members say there were other witnesses who still have yet to come forward.

The last known video of Nancy showed her waving as she paddled. She was reportedly in a tour group of 10 on Lake Atitlán but disappeared hours after she was seen on video.

“There are people that witnessed what happened, within the group, that haven’t come forward,” Nancy’s sister, Nicky Ng, told ABC News. “We’re racking our brain as to why they wouldn’t want to come forward and help if nothing nefarious happened.”

Guatemala’s Navy stopped searching for Nancy after 72 hours, prompting the family to hire private search teams that combed through the area. Now, the family is raising money to help cover the costs of those private search efforts, through a  GoFundMe page.

Black Wolf Helicopters search team joined in the search, while the FBI and the U.S. Department of State has joined Guatemalan authorities in the investigation

“We’ve searched 99% of the lake — that’s was with helicopters, drones, boat crews,” Black Wolf Helicopters owner Chris Sharpe said.

Sharp told ABC 7 that, for him, the case has become “a criminal investigation because the witnesses who were there at a material time are not being forthcoming.”

Ng, according to family members, is a graduate of California State University (Los Angeles) and works with special needs children at the Alhambra Unified School District in Southern California.

Check back for updates.

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[Feature Photo: Nancy Ng/Family Handout]

Additional reporting by Jonathan Anderson and KC Wildmoon