The U.S. government is launching two new media campaigns to try to stop immigrants from attempting clandestine border crossings (search) and trying to sneak children into the country in car trunks, engines and even gasoline tanks.

One ad unveiled Thursday shows a young girl gasping for air inside a car trunk while her mother bangs desperately on the lid as the vehicle sits snarled in traffic.

Others invoke images of a graveyard and a funeral procession.

The U.S. Department of Homeland Security announced some of the ads Thursday at San Diego's San Ysidro border crossing, the nation's busiest.

The Spanish-language public service announcements call attention to what authorities say is the alarming practice of smugglers (search) stuffing children into vehicle compartments that could become death traps.

Their release coincided with the launch of another media campaign by the U.S. Border Patrol to call attention to the dangers of clandestine border crossings.

Those television spots, which began airing last week in the Mexican state of Michoacan, and were due to begin this week in U.S. cities, including Los Angeles, Chicago and Houston. The campaign unveiled Thursday will target cities closer to California's Mexican border (search).

The federal government has campaigned against illegal border crossings before, but this is one of its more ambitious efforts.

The Border Patrol's $1.5-million campaign, called No Mas Cruces en La Frontera, or No More Border Crossings, is the first time the agency has bought airtime, said Gloria Chavez, one of the organizers.

One of the ads shows a graveyard and ends with a narrator's warning in Spanish: "There are many reasons to cross the border. None is worth your life." Another recreates a small-town funeral for a Mexican man who died in the desert.

Migrants who heard or watched the anti-smuggling ads at a Tijuana, Mexico, shelter Wednesday night said they were accurate, even powerful. But they vowed to return to the United States anyway.

Agustin Jaime Ortiz, 33, said the warnings against hiding inside vehicles were "100 percent effective," stirring memories of a previous crossing inside a meat freezer truck. He remembered turning purple on the 1994 trip from Tijuana to Los Angeles.

Authorities are especially worried about the risk for children. Inspectors once found a 14-year-old girl strapped under the metal bars of a car seat, and also discovered a young boy hidden inside a gas tank, his jeans and T-shirt soaked with fuel. On another occasion, a 3-year-old girl had been hidden inside a pinata.

Nearly 6,500 children were taken into custody at California border crossings in the 12-month period ending Sept. 30, 2004, a 17 percent increase from the previous year, according to the U.S. Customs and Border Protection bureau's San Diego office.

Since October, authorities at the San Ysidro border crossing say they have discovered nearly 300 different vehicle compartments used to smuggle immigrants.

The campaigns come as heightened border enforcement in and around San Diego and El Paso, Texas, over the last decade has forced migrants to take bigger risks, whether crossing through unforgiving Arizona deserts in the summer or stuffed inside vehicle dashboards.

The Mexican government has published a comic-book style booklet warning of the dangers of border crossings, but the publication has been criticized by some in the United States because it also shows safe ways to cross.