Melissa Shirley Casias

Melissa Shirley Casias was an active administrative assistant at Los Alamos National Laboratory, the premier nuclear weapons research facility in the United States. She was 53 years old and is believed to have held top security clearance. On June 26, 2025, she vanished from her home in Ranchos de Taos, New Mexico – less than two months after Anthony Chavez, a retired LANL employee, disappeared from his home in Los Alamos under nearly identical circumstances.

Both left on foot. Both left behind their car, keys, wallet, and phone. Neither has been found.

Background

Casias lived in Ranchos de Taos, a community in Taos County, New Mexico – roughly 90 miles north of Los Alamos. She commuted to the laboratory for work. The specific nature of her administrative role has not been publicly detailed, but LANL administrative staff with top security clearance typically handle classified documentation, scheduling for restricted programs, or support for personnel involved in weapons research.

She lived with her husband Mark and their daughter Sierra.

What Happened

On the morning of June 26, 2025, Mark Casias dropped his wife off at Los Alamos National Laboratory around 6:15 a.m. She told him she needed to complete a work task and would return the car by 11 a.m.

However, Melissa returned home to Ranchos de Taos – over an hour away – around 7:45 a.m., telling her daughter she had forgotten her badge. She decided to either work from home or call out for the day.

Around 12:30 p.m., Melissa picked up a Subway sandwich and met Sierra briefly in Taos Plaza between 12:50 and 12:57 p.m. Sierra gave her mother a check to deposit at the bank. Melissa left. That was the last time her daughter saw her.

When Melissa didn’t return with the car by 11 a.m., her boss called Mark in the afternoon to ask if she was okay – revealing she hadn’t shown up to work that day. All of Melissa’s belongings – her car, purse, and phones – were later found inside her home.

She was last seen walking eastbound on a highway in Talpa, a small community adjacent to Ranchos de Taos.

The Search

The New Mexico State Police launched a search, coordinating with local agencies. The case was reported to the state’s Missing Persons database. Despite sustained efforts, no trace of Casias has been found.

What Doesn’t Add Up

The timeline of Casias’s last day contains details that resist easy explanation. She drove over an hour home from LANL, saying she forgot her badge. She met her daughter for seven minutes in Taos Plaza, handed over a check, and left. At some point after that, she left her car, purse, and both phones inside her home and walked away on foot – eastbound on a highway.

The parallel to Anthony Chavez is striking. Two people connected to Los Alamos National Laboratory, vanishing from New Mexico within weeks of each other, both leaving on foot, both leaving behind all personal effects. Chavez was retired. Casias was active and held security clearance. Neither has been found.

The Daily Mail reported in April 2026 that the dual disappearances had drawn congressional attention. Rep. Tim Burchett told the paper: “The numbers seem very high in these certain areas of research. I think we’d better be paying attention, and I don’t think we should trust our government.”

Sources

1. “New Mexico State Police Continue Search For LANL Employee Melissa Casias Of Ranchos de Taos,” Los Alamos Daily Post, 2025.
2. “New Mexico State Police Seeks 53-Year-Old Melissa Shirley Casias Missing From Taos Since June 26,” Los Alamos Reporter, July 7, 2025.
3. New Mexico Missing Persons Database – Melissa Casias
4. “53-year-old Melissa Casias missing from Talpa, New Mexico, since June 26,” NBC News Dateline, 2025.
5. Daily Mail – Mystery surrounds death of NINTH scientist tied to US secrets (April 7, 2026).