Nancy Ng update: Family of woman who went missing in Guatemala urges key witnesses to speak up

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The family of a Southern California woman who disappeared in Guatemala is urging the last two people to see her alive to speak to investigators.

Nancy Ng, of Monterey Park, hasn't been seen since Oct. 19. It is believed she went out on a kayak with a yoga group 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.

"I personally request that these individuals present themselves to their local Law Enforcement Department at the earliest opportunity," said the search team coordinator in a statement released Saturday on behalf of Nancy's family.

The family says Guatemalan and United States authorities know the two witnesses' names. Last week, the owners of the kayak company who rented out the kayaks to the group spoke out, sharing details on what happened after the excursion was over.

Lee and Elaine Beal, owners of Kayak Guatemala, said the yoga group Nancy was with "didn't say a word" to them after the excursion and left their hotel about 12 hours later.

READ MORE | Kayak company speaks out after SoCal woman goes missing in Guatemala

Lee and Elaine Beal, owners of Kayak Guatemala, said the yoga group Nancy Ng was with "didn't say a word" to them after the excursion and left their hotel about 12 hours later.

A helicopter company hired by Nancy's family plans to resume their search this week.

Guatemalan government prosecutors believe she went swimming and drowned.

The FBI is now involved in the urgent search for Nancy Ng, a Southern California woman whose family says she disappeared while on a yoga retreat in Guatemala around Oct. 19.

Nancy's family sent a statement to ABC News last week, saying "Our family has tried to contact the witness many times over the last three weeks but she will not speak with us. The police report we received did not include a direct statement from her either. Her silence has hindered our search efforts and left us in the dark about what happened to Nancy. We don't know which nightmare scenario to believe."

Nancy worked with special-needs children in the Alhambra Unified School District. They describe her as a person who is loving and full of life.