A Mexican woman who arrived on a flight from the US has been living at the airport in the Caribbean resort city of Cancun since June 30, officials said.
Marcela Silvia Montaño Mancera, a Mexican citizen, is being watched by police but cannot be arrested because she has not committed a crime, Federal Police officers told EFE.
Airport workers spotted the 45-year-old woman wandering through the terminals, sleeping on the floor, washing in the restrooms and withdrawing money from an ATM to pay for meals at the airport restaurants.
"She looks like a regular passenger at first glance, people don't look at her, but we have seen her every day ... we are not doctors, but it's obvious that she has problems, some of my co-workers tried to speak with her, but at times it seems as if she loses it," an airline worker said.
The woman has not caused trouble, but she walks around speaking to herself in Spanish and English, said a police officer.
A "routine inspection" found that the woman is carrying a Mexican passport in the name of Marcela Silvia Montaño Mancera, who was born May 2, 1968, a police spokesman said.
Officials are trying to locate the woman's family but have not had any luck, the police said.