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Mexican authorities have detained the owner of a Mexican oil services company who allegedly defrauded Citigroup of up to $400 million and may have used his professional soccer team to launder money, a top official said Monday.

Amado Yáñez is being held under a form of house arrest that allows authorities to hold him for up to 40 days without charges, Attorney General Jesus Murillo Karam said. He said authorities had found evidence of wrongdoing but they continue to investigate.

The case has threatened to put on hold Mexico's much-touted reform of the state-owned oil industry, which would allow private companies to drill for the first time in 75 years. The conservative National Action Party, whose votes are needed to pass enabling legislation for the reform, has refused to continue discussions on the bill until the Yáñez case is fully investigated.

National Action was in power for more than a decade beginning in 2000, when Yáñez's Oceanografia company started getting showered with big contracts from the state-owned Petroleos Mexicanos company. The party, now in the middle of internal leadership elections, has voiced concerns that current President Enrique Peña Nieto may be using the case to smear National Action politically.

The issue arose when Citigroup's Mexican subsidiary, Banamex, said Oceanografia overstated by $400 million the business it was doing with Pemex. Oceanografia used falsified invoices as collateral for $585 million in loans from Banamex, Citigroup said. But after an investigation, Citigroup could only verify $185 million of invoices.

Mexico's government has taken administrative control of Oceanografia to try to get workers paid and to recover the missing millions. Armed with a powerful fleet of service boats in the Gulf of Mexico, the company has provided construction and services to Pemex's offshore oil platforms.

Yáñez also owns a team in Mexico's first division soccer league, the White Roosters based in the central city of Queretaro. The team said in a statement that federal authorities have taken over its offices and are expected to name an administrator for the squad. Officials are investigating whether some of the defrauded money may have been channeled into or though the team's finances.

Murillo Karam denied there are political motivations behind the investigation.

"This is about a company damaging a bank," he said. "There is no political overtone in this investigation."

He also said he didn't understand National Action's decision to retreat from energy reform talks until the investigation runs its course.

National Action president Cecilia Romero said, "We need that clarity before we move on with these transcendental reforms."

A failure to resume talks would leave Peña Nieto's Institutional Revolutionary Party without the votes needed to pass the reform, which he says would bring in private involvement needed to revive Mexico's declining oil production.

Ruben Aguilar, who served as spokesman for the first National Action president, Vicente Fox, suggested the investigation should focus not only on politicians, but also bank employees and Pemex officials who might have been involved in a scheme so complex it took Banamex months to realize it was being fed false collateral.

"The main thing is, it appears to me, is that this couldn't have happened without corruption in the bank and Pemex," Aguilar said.

He also suggested that National Action may have walked out of the talks because Peña Nieto's party, which includes a lot of old-guard oil union leaders, may have gotten cold feet about the reform originally pushed by National Action.

"They're trying to tone it down a bit in the enabling legislation," Aguilar said.

Federico Estévez, a political science professor at the Autonomous Technological Institute of Mexico, said the investigation might actually help the energy reform, given the longstanding reports of corruption and sweetheart deals in the country's oil industry.

"I wonder if this isn't actually good down the long haul for the foreign investors, meaning that they'll see that .... the kind of shenanigans of the past will be less likely to be tolerated," Estévez said.

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