MEXICO CITY — She offered 59 brand new Hummers to regional union leaders to buy their loyalty. Mexican newspapers have closely tracked her displays of wealth, from California mansions and $5,000 Hermès bags to noticeable shifts in her looks as she went under the knife.

But the love for luxury flaunted by Elba Esther Gordillo, the most powerful woman in Mexico, might have been her undoing. She was arrested Tuesday night on suspicion of embezzling $200 million in union funds for her personal use, including plastic surgery, multimillion-dollar spending sprees at luxury department stores and those seaside mansions near San Diego.

In court papers on Wednesday, Mexican prosecutors said her web of financial subterfuge, filtered through intermediaries and American and Swiss banks, was an act of organized crime. Investigators searched her apartment in an upscale Mexico City neighborhood on Wednesday.

During a brief court hearing, Ms. Gordillo, dressed in a simple T-shirt and beige pants, stared out bitterly from behind the bars of a prison courtroom as the charges were read against her. She declined to make any statement.