Nancy Ng hasn't been seen since Oct. 19. It is believed she went out on a kayak on Lake Atitlán that day, but many of the witnesses who may have more information about her activities reportedly have not been cooperating with investigators.
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Ng's family hired a private search team, who said they scoured much of the area of the lake by air and underwater but found no sign of her.
The Guatemalan government says 95% of the lake was searched and those efforts have now halted.
Guatemalan government prosecutors believe she went swimming and drowned.
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But Nancy's family says that information conflicts with the evidence they received from their attorney and search and rescue team.
According to a statement Guatemalan prosecutor's office provided to ABC News, Ng was traveling with a U.S.-based tour group. She went out on the kayaking trip and, according to a woman she was with, they advanced "approximately 2 kilometers deeper into the lake, where the missing woman tells" the witness that "she wants to swim and that is when she drowns," the statement said.
Why it took that woman and the tour group 24 hours to report the incident to authorities remains a mystery.
Family searching for answers after SoCal woman disappears in Guatemala
Local fire and rescue officials told ABC News that there were reports that Ng was last seen about half-a-mile away from the shore. Her kayak was later found, but there was no sign of Ng, a fitness enthusiast.
Her family says Ng works with special needs children in the Alhambra Unified School District. They describe her as a person who is loving and full of life.