MEXICO CITY (AP) — Mexican authorities have detected many strange schemes to smuggle Central American migrants to the U.S. border, but on Saturday they said they found a new one: a fake ambulance loaded with 28 Nicaraguans, including nine unaccompanied children.

Mexico’s Interior Department said the vehicle had been painted with fake logos from a government hospital network. The vehicle was stopped in the Pacific coast state of Oaxaca.

The National Migration Institute said the driver had tried to pass himself off as a health care worker and was detained.

Migrants found in such circumstances are usually returned to their home countries, unless they are the victims of a crime.

Immigrant traffickers in Mexico general try to smuggle migrants in buses or freight trucks. The trucks are often painted with the logos of well-known companies to try to avoid scrutiny.