Mexico captured a suspected drug trafficker with links to the country's most wanted man, Sinaloa cartel boss Joaquin Shorty Guzman, whose operations have recently suffered a string of blows.

Mexico's federal police said on Wednesday they captured Luis Rodriguez Olivera, known as El Guero (Blondie), for whom U.S. authorities have offered a reward of up to $5 million.

In a statement, Mexican police said Rodriguez Olivera and his brothers were responsible for trafficking cocaine to the United States between 1996 and 2008 for Guzman's gang.

A wanted statement on the U.S. State Department's website said Rodriguez Olivera and his brothers split with the Sinaloa cartel around 2005 and later forged a strong relationship with Guzman's rivals, the Zetas cartel.

One intelligence official, speaking on condition of anonymity, said that the 39-year-old Rodriguez Olivera had ties to Guzman but had latterly struck out on his own. Federal police arrested him on Tuesday in Mexico City airport.

Later on Wednesday, the government said it had seized eight containers carrying more than 120 tonnes of monomethylamine in the Pacific port of Lazaro Cardenas in Michoacan state.

It was the second big seizure announced this week of monomethylamine, a compound used to make methamphetamines. According to calculations by security analysts, the shipment could have been worth $300 million dollars or more.

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President Felipe Calderon's conservative administration has been dominated by a military crackdown on drug cartels that has claimed more than 46,000 lives in the past five years, eroding support for his National Action Party, or PAN.

The PAN has trailed its main rival for months as Mexico gears up for a July 2012 presidential election, and analysts say it needs to rack up some victories in the fight on drugs.

Javier Oliva, a drug war expert at the National Autonomous University of Mexico (UNAM), said Michoachan-based cartel La Familia was the most likely intended recipient for the Lazaro Cardenas shipment, though the Zetas were also a possibility.

The shipment set out from Shanghai and was destined for the Guatemalan port of Puerto Quetzal, the government said.

Though the Sinaloa cartel deals in methamphetamines, it is not regarded as exercising much control over Lazaro Cardenas.

Mexico had already arrested three senior traffickers allied to Guzman in the past three months.

(Editing by John O'Callaghan)