(Adds comment from government official, adds details on house)
By Dave Graham and Anahi Rama
LOS MOCHIS, Mexico, Jan 11 (Reuters) - A secret meeting Hollywood star Sean Penn held with the world's most-wanted drug boss, Joaquin "El Chapo" Guzman, to discuss a magazine article was essential to finding the fugitive, Mexico's attorney general said on Monday.
Guzman, head of the Sinaloa drug cartel, was captured on Friday following a months-long manhunt after he tunnelled out of a Mexican maximum security prison in July.
Mexico has said it plans to extradite him to the United States, where he is wanted for exporting hundreds of tonnes of cocaine, methamphetamine and heroin across the border.
The media were on Monday granted access to the house where Guzman was holed up before his capture. Yet again, he escaped into a tunnel for a few hours, leaving behind a building that was a shambolic mess of bullet holes, bloodstains and decaying food.
Mexican Attorney General Arely Gomez said while extraditing kingpins takes on average a year, it could take up to five years in Guzman's case. Still, speaking on condition of anonymity, another senior Mexican official later said the government had no interest in letting the process drag out.
Rolling Stone magazine published an article by Penn on Saturday based on his interview with Guzman. Gomez said a line of investigation had been opened into the meeting between Guzman and Penn in early October at a jungle hideout, adding that any possible criminal investigation against the actor-director would depend on what, if any, deals he struck with Guzman.
U.S. investigators will also examine Penn's interactions with Guzman, two U.S. government sources said on Monday, but it was unclear if prosecutors would try to force the actor to turn over information about the interview.
Mexican actress Kate del Castillo accompanied Penn to the meeting at an undisclosed location. Mexico's government had been following a Guzman lawyer who accompanied them. Mexican daily El Universal published photographs on Monday of Penn and Castillo that it said showed the pair being tracked at the time.
"It (the meeting) was an essential element, because we were following (Guzman's) lawyer, and the lawyer took us to these people and to this meeting," Gomez told local radio.
Penn, who has been criticized in the United States and in Mexico for visiting Guzman, told the Associated Press on Monday: "I've got nothin' to hide."
Reuters could not reach del Castillo for comment.
In the interview with Penn published by Rolling Stone, Guzman said he felt neither remorse nor responsibility for smuggling billions of dollars worth of drugs into the United States. Nor did he consider himself a violent man despite countless murders blamed on him, he told Penn.
MIRROR HID ESCAPE TUNNEL
The drug kingpin initially gave Mexican security forces the slip as they staged a dawn raid on Friday, opening a secret door hidden behind a mirror in his walk-in bedroom closet, and descending into a tunnel about 30 meters long that connected to the drains of Los Mochis, a city in his native state of Sinaloa.
He spent hours below ground as his henchmen lured pursuing Marines into a chase onto the roof of the house and into neighbouring properties, where four of them were shot dead. Another was killed inside the house, officials said.
Finally discovering the hidden tunnel, some Marines tried to follow Guzman into the drains, but could not find him, a security official said. As rain started to fill the drains, Guzman eventually emerged from a manhole by a gas station about a mile (1.6 km) across town and stole a car at gunpoint.
He and the henchman who fled with him dumped the first car for a second, but were soon caught by federal traffic police chasing down the stolen vehicles, a security official said.
"My holidays are over," Guzman said when he was finally caught, Televisa reported.
Video footage broadcast by Televisa showed Marines firing shots inside the house after they stormed through two doors to find 15 of Guzman's henchmen armed with machine guns and rocket launchers. The military operation was dubbed "Black Swan".
It took the Marines 90 minutes to discover the tunnel entrance, giving Guzman a crucial head start, the broadcaster said. The lever to open the reinforced door behind the mirror was concealed in the light of the walk-in closet.
Below was a submarine-like metal hatch connecting the partially flooded tunnel to the Los Mochis drains.
Upstairs, bullet holes peppering the stair wall and thick smears of blood in several rooms of the debris-strewn house testified to the brutal shootout that had taken place. Clothes, food and equipment were scattered throughout, and socks, shirts and underpants still hung on a washing line on the terrace.
In the bedroom were flatscreen TVs and a sofa littered with injectable testosterone, syringes, antibiotics and condoms. There was also a packet of "Miracle V Tonic", a dietary supplement promising to enhance sexual performance.
Inside the bedclothes of one of the beds were DVDs of "La Reina Del Sur," a fictional series about a female drug boss starring actress del Castillo.
Marines found another hole beneath a refrigerator which proved to be a red herring, the apparent beginnings of a project to build another escape route. They also found two women cowering in one of the home's five bathrooms.
WANTED IN THE UNITED STATES
The White House on Monday commended Mexico's government for Guzman's capture, stressing it had been a key bilateral issue.
"The capture of Mr. Guzman has been a high priority for both Mexico and the United States," White House spokesman Josh Earnest said at a news briefing.
The Mexican government said late on Sunday it was formally starting extradition proceedings against Guzman. Mexico regularly extradites leading traffickers but the government resisted handing over Guzman after his arrest in February 2014 as a point of national pride.
On Sunday, Interpol served two extradition warrants, the Mexican attorney general's office said, kick-starting the latest attempt to have Guzman face U.S. justice.
The U.S. government wants Guzman, who is believed to be 58 years old, tried on charges ranging from money laundering to drug trafficking, kidnapping and murder.
Guzman, who is blamed for thousands of deaths in Mexico and the United States from addiction and gang warfare, is facing open federal indictments in seven U.S. jurisdictions.
Chicago, which dubbed Guzman its first Public Enemy No. 1 since Al Capone in 2013, and Brooklyn, New York, are top contenders to host what would be one of the highest-profile U.S. trials in years, former U.S. law enforcement officials said.
(Reporting by Frank Jack Daniel, Alexandra Alper, Veronica Gomez and Christine Murray in Mexico City, Tracy Rucinski in Chicago, Mica Rosenberg in New York and Mark Hosenball and Doina Chiacu in Washington; Writing by Simon Gardner; Editing by Frances Kerry, Cynthia Osterman, Lisa Shumaker and Michael Perry)
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