American officials who had been tracking the world’s most notorious drug lord were afraid that he had slipped through their grasp one more time.

The DEA, ICE and the U.S. Marshals had been tracking cellphones used by associates of Joaquin “Shorty” Guzman, AKA El Chapo, the head of the Sinaloa drug cartel, and by last Monday they had traced him to his ex-wife’s house. Guzman was wanted in six different U.S. courts for allegedly smuggling billions of dollars of cocaine, meth, heroin and marijuana across the border and had a $5 million U.S. pricetag on his head.

But just before Mexican Marines raided the home in Culiacan, Mexico, Guzman slipped through a secret door beneath his bathtub and into the city sewer system. And most of the wiretapped phones went dead.

“At this point the phones went out of service,” said a U.S. law enforcement official. “It’s likely he was tipped.”

One of the phones remained active, however. “It led us to Mazatlan,” said the official.

Early Saturday morning, Mexican Marines arrested Guzman, 59, and several associates at a condo tower in the beach resort town of Mazatlan, 220 kilometers south of Culiacan, ending a 13-year manhunt for the largest importer of drugs to the U.S. – and years of frustration for U.S. law enforcement.

Chapo Guzman had been on the lam since 2001, when he escaped in a laundry cart from a Mexican prison. The hunt for Guzman intensified after 2007, when then-Mexican president Felipe Calderon launched a war against the nation’s drug cartels. Eighty-thousand people have died since 2007 in a multi-front war between the Sinaloa, Gulf and Zetas cartels and the Mexican government.

The U.S. has been supplying information from wiretaps to Mexican officials for many years. But each time they tracked Guzman to a specific location, and told Mexican authorities were to look, their quarry escaped. In 2012, the U.S. pinpointed Guzman’s address in Los Cabos, only to watch as he eluded capture yet again.

“Every time he gets away, they tell us, ‘He got out the back door,’” one American official told reporters at the time. The official said that Americans involved in the manhunt had started to joke that there was “no word in Spanish for surround.”