Little Douglas Ramirez of Guatemala was crying as the preschooler and his two older sisters, ages 10 and 13, were picked up by border agents last week along a highway just north of the Rio Grande.

That was where they were abandoned by the smuggler who had brought them across the Mexican border to reunite them with their father in the U.S. for the holidays.

Immigration officials in Texas say the annual holiday surge in children crossing the border illegally is on.

Illegal immigrants working in the United States sometimes arrange for friends, relatives or professional smugglers to sneak their youngsters into this country.

In some cases, the smugglers try to slip the children across the Rio Grande and through the brush along lightly guarded sections of the border; that was what happened with the Ramirez children.

In other instances, adults pretend to be the youngsters' parents and try to drive across the border bridges during the busy holiday season, claiming they are visiting relatives or going shopping in the United States.

"As the holiday season is already upon us, so also is the season for child smuggling," said David Higgerson, director of the port of entry at Hidalgo, Texas.

Three Houston residents were arrested last week at the Hidalgo international bridge for posing as the mother and grandparents of a 2-year-old Mexican boy. The boy was groggy from an apparent dose of a pain-relieving syrup, administered to keep him quiet as they went through customs.

A few days before, a 24-year-old woman was arrested at the bridge for trying to pass off as a U.S. citizen a 10-year-old Mexican she said was her nephew.

Late fall is a peak time to make the attempt, because of the desire among many families to be together during the holidays, and because many parents who crossed over early in the year for the growing or construction season have saved enough money and established themselves enough to send for their kids.

Children who are caught on the bridges are sent back to shelters on the Mexican side to wait for family members to claim them. Those caught on the U.S. side, such as Douglas and his sisters, are usually sent to American shelters, and after a lot of red tape, many are ultimately released to their families in this country, even though the parents are illegal immigrants.

But the risks are considerable, for the families, their children and the adults who try to smuggle the youngsters in.

In some cases, depending on the federal agency or the particular officer involved, the illegal-immigrant parents can be taken into custody when they show up to claim their child, and the whole family can then be deported.

As for entrusting children to professional smugglers, "if they're young girls they could be raped. Little boys can be sold to other families," said Nina Pruneda of U.S. Immigration and Customs Enforcement. "They could be kidnapped, held for more money. Some actually make it, end up with their families, everything's happy. Others don't."

The adults who try to bring children across are often well-meaning relatives or acquaintances who often end up being charged with a crime and having their vehicle seized.

At the Hidalgo port alone, customs officers have stopped 24 child-smuggling attempts since the 2007 fiscal year began Oct. 1, Higgerson said. Customs spokesman Rick Pauza said Laredo's two bridges saw 218 child smuggling attempts during fiscal year 2006, many of them during the holidays, though he did not have a month-by-month breakdown.

Martha Newton, director of the U.S. Office of Refugee Resettlement, said 65 percent of the approximately 8,000 children sheltered yearly across the nation end up released to someone in the United States.

"We will release to undocumented sponsors," she said, referring to parents who are not citizens. "We are not the Department of Homeland Security. We're in charge of the best interests of the child."

On Monday, a happy, playful Douglas sat in a big chair next to lawyers and Texas social workers, peeking around and smiling joyfully at a man claiming to be his uncle and a man he did not seem to know as well, who said he was the father.

That man, a Fort Lauderdale, Fla., restaurant worker named Maximo Lemus Andrade, carried family photos and documents that had been faxed from Guatemala. A family court judge ordered paternity testing and a check of the documents and said the child would stay in foster care until a hearing in January.