Drug cartels are using classified job ads to lure young Mexicans near the U.S. border into unknowingly working as drug couriers, law enforcement officials said Thursday.

Mexico City's El Universal newspaper first reported the trend Thursday, saying ads in some Ciudad Juarez newspapers require applicants to have the U.S. visa needed to drive a vehicle across the border but do not mention job experience.

"A lot of times they advertise as if they were a company, and they send them to El Paso but they don't tell them what they are carrying," an official at the federal Attorney General's office in Ciudad Juarez told The Associated Press. He was not authorized to be quoted by name.

The official said applicants often think they are applying to become messengers, but they end up unwittingly driving vehicles loaded with drugs into neighboring El Paso, Texas.

"They often list jobs as 'messengers,' or simply say 'jobs available' or 'here's an opportunity,"' the official said. "They tell them they have to take some documents to El Paso, but they don't tell them what they are really carrying."

The newspaper El Universal cited one such ad as saying: "We are looking for students with valid passports and visas to work during spring break. We offer well-paying jobs."

Tighter border security on both sides has forced drug cartels to find creative ways to move their contraband into the U.S.

Chris Mears, a spokesman for the El Paso Police Department, said he was aware of the trend.

"There have been quite a few teenagers who have been charged over the last couple of years with loads of drugs in their vehicles," Mears said. "Some of them have had (criminal) backgrounds, some of them haven't."

Mears said people in border areas should already know that driving a vehicle across the border for someone else could land them in trouble.

"If it's not your or your family's car, don't drive it across the border," Mears said.