MEXICO CITY — 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 Yanez 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 Yanez case is fully investigated.

National Action was in power for more than a decade beginning in 2000, when Yanez’s Oceanografia company started getting big contracts from the state-owned Petroleos Mexicanos company. The party has voiced concerns that current President Enrique Pena 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.