Guzman, 54, the multibillionaire fugitive head of the Sinaloa cartel , married Coronel the day she turned 18 at a lavish wedding in the highlands of central Mexico in 2007. She is believed to be his third or fourth wife and is a niece of Ignacio “Nacho” Coronel, a one-time partner of Guzman who was killed in July 2010 in a shootout with the Mexican army.

Turns out Coronel, a 22-year-old former beauty queen, holds U.S. citizenship, which entitles her to travel freely to the U.S. and to use its hospitals. By being born to a U.S. citizen, not to mention in California, her little girls now also have U.S. citizenship.

Emma Coronel traveled to Southern California in mid-July, and on Aug. 15 gave birth to twin girls at Antelope Valley Hospital in Lancaster, according to birth records and a senior U.S. law enforcement official.

REPORTING FROM MEXICO CITY -- The spaces for “Name of Father” are blank. But the L.A. County birth certificates list the mother, who happens to be the young wife of one of history’s biggest and most sought-after drug lords, Joaquin “El Chapo” Guzman.

This post has been updated. See the note at the bottom for details.

U.S. federal agents apparently kept tabs on Emma Coronel even before she crossed the border at Calexico, through her hospital stay and until she left the country to return to Mexico. Although her husband tops most-wanted lists on both sides of the border, Coronel was not arrested because there are no charges against her, the law enforcement official said.

While she no doubt could have provided useful information on her husband’s whereabouts, drug agents have said the problem with apprehending Guzman has less to do with finding him and more with how Mexican troops can seize him. He surrounds himself with enormous bands of well-armed security and tends to stick to isolated, mountainous regions that are difficult to reach, agents say.

Coronel’s presence in the Los Angeles area and other parts of Southern California did not seem to attract attention. At the Antelope Valley Hospital, a spokeswoman declined to comment, citing privacy rules.

Birth certificates show the girls were born Aug. 15 at the Lancaster facility. The first came into the world, at 3:50 p.m. Her sister followed at 3:51.

In the spaces for the mother’s signature, Coronel opted to print her name.

Guzman, whose nickname means “Shorty,” is about 5 feet, 6 inches tall. He was arrested in 1993, but escaped prison in 2001 by bribing guards to hide him in a laundry basket.

U.S. authorities have placed a $5-million bounty on Guzman’s head and allege he and the Sinaloa cartel now control the bulk of cocaine and marijuana trafficking into the U.S. from Mexico and Colombia. Guzman’s forces last year moved into Mexico’s northeast shoulder around the border state of Tamaulipas, and he may currently be behind a ferocious push of gunmen into the coastal state of Veracruz to challenge the Zetas gang that dominates there. Scores of people have been killed or gone missing in recent days.

Coronel is said to have first caught Guzman’s eye when she entered the regional Miss Coffee and Guava beauty contest. He made his interest known, and she was crowned queen of the pageant. They married a few months later.

Updated, 8:30 p.m. Sept. 26: The post was changed to remove some personal information.

Updated, 7:25 p.m. Sept. 27: The post was changed to clarify that the children are eligible for U.S. citizenship because of their mother's citizenship, not only because they were born in California.

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-- Tracy Wilkinson and Ken Ellingwood

PHOTO: Joaquin Guzman in Almoloya, Mexico's high security jail in a June 2000 photo. CREDIT: Heriberto Rodriguez/Reuters