An increasing number of illegal immigrants who left their children back home are hiring complete strangers to bring the youngsters into this country by bluffing their way past U.S. border inspectors.

Typically, the stranger poses as the child's mother or another relative as she drives through a checkpoint. Sometimes the children are given cough syrup to sedate them and ensure they don't say or do anything to make border guards suspicious.

U.S. officials say they are seeing more such cases because stepped-up enforcement along the border has made it more dangerous to sneak into the country by trekking across the desert.

"People who may be afraid or think it's too dangerous to bring a child through the desert when it's 120 degrees think it's better to place a child in the hands of a total stranger," said Roger Maier, a U.S. Customs and Border Protection spokesman in Texas.

U.S. officials warned that entrusting children to a stranger is foolish, too.

"There's no guarantee that you're going to be reunited with your child. There's no guarantee that your child is being cared for," said Brian Levin, a U.S. Customs and Border Protection spokesman in Arizona.

Nevertheless, officials at the border could not cite a specific case of a child being hurt or stolen in the smuggling scheme.

Dozens of U.S. citizens, permanent residents and other women with a legal right to be in this country have been prosecuted in the past few years for trying to smuggle children into the U.S. Border officials said they do not have exact numbers but believe such cases are on the rise.

The women are typically poor, and are hired by smugglers for $100 to $500 for the transaction. They are often mothers themselves, and use their own children's birth certificates when they drive through a checkpoint.

"They're a vulnerable class of people who get sucked into this," said Joel Parris, an assistant federal public defender in Tucson who has defended several women smugglers. "These women are so focused on surviving and taking care of their own kids, when someone comes with a pity trip, their sympathy is so strong they can't resist."

Ana Meza-Montano, a 36-year-old single mother from Agua Prieta, Mexico, across the border from Douglas, Ariz., had a border crossing card that allowed her to enter the United States for short periods to shop and run other errands.

Meza-Montano was caught at the Douglas port of entry trying to smuggle a 1-year-old girl who she said was her daughter.

Parris, who defended her, said Meza-Montano agreed to the transaction because a smuggler offered to pay off her son's $100 bicycle, which was on layaway at a Wal-Mart. The woman is serving a 15-month prison sentence.

Sandra Ramirez, a 24-year-old single mother of four, was caught trying to sneak an 11-year-old boy through the Nogales, Ariz., port of entry, and said a co-worker offered her $1,000 to do it. Now Ramirez is serving a 15-month prison sentence and will be deported to Mexico after she gets out.

"This is just one of the most overwhelmingly saddest cases," said Ramirez's lawyer, Stephanie Meade. "She had no idea of the kind of consequences and trouble that she would get in."

Officials say the smuggling tactic has become more common partly because more illegal immigrants are deciding to bring their families into the country. In the past, it was more common for men to leave their families behind and return periodically for visits.

Also, because of tighter enforcement by the Border Patrol and the National Guard, illegal immigrants who want to sneak across the desert are being forced to make the attempt along more remote, more rugged — and more dangerous — stretches of the border.

The U.S. Attorney's Office in Arizona has made prosecuting these child-smuggling cases one of its top priorities.

"Children are being put in situations where the risk of something happening to them is high, and we felt that people need to be held accountable for this," spokesman Wyn Hornbuckle said.

He added: "There are many examples of how violent these smuggling organizations are and how ruthless they've become, and they'd be the last people I'd entrust my kids to."