By Luciana Magalhaes 

SÃO PAULO--The judge presiding over the criminal trial of Brazilian businessman Eike Batista is under investigation for allegedly driving a luxury vehicle he ordered seized from the former tycoon, conduct that could help pressure the magistrate's removal from the high-profile case.

An appeals court in Rio de Janeiro on Tuesday opened the probe after local newspapers published photos of a man identified as Federal Judge Flávio Roberto de Souza piloting a white Porsche Cayenne through the streets of the beachside city. The Porsche had been taken from Mr. Batista earlier this month by federal police.

Once Brazil's richest person, Mr. Batista is on trial for insider trading related to the financial meltdown of his oil company, formerly named OGX Petróleo e Gás Participações S.A. He and his attorneys have repeatedly denied wrongdoing.

Following an order by Judge de Souza, authorities this month seized 11 vehicles from Mr. Batista, including the Porsche and a Lamborghini Aventador, along with jewelry, a piano and a fake Fabergé egg, as guarantees to repay investors in the event the entrepreneur is found guilty. The cars were to be sold at auction and the proceeds placed into escrow until the conclusion of the trial, an action allowed under Brazilian law.

The court on Tuesday suspended two public auctions of Mr. Batista's seized vehicles scheduled for Feb. 26 and March 9.

Judge de Souza didn't respond to a request for comment from The Wall Street Journal about the investigation into his alleged conduct.

In a note published Tuesday on the website of Brazilian magazine Veja, Judge de Souza admitted driving the Porsche. He told the magazine that the car had been stored for safekeeping in the garage of his apartment building because there wasn't sufficient space for all of Mr. Batista's vehicles at the federal court lot in Rio de Janeiro.

The judge told Veja that he was returning the Porsche on Tuesday to the federal court parking lot in preparation for auction after a court driver was unable to perform the task. He said authorities were aware the Porsche was parked at his building.

Authorities investigating Judge de Souza couldn't immediately confirm whether there was a shortage of parking spaces at the federal court lot.

Judge de Souza had already been under fire by lawyers for Mr. Batista, who have requested the magistrate's removal from the case for alleged partiality against their client. The lawyers claim that the judge has given a number of press interviews in which he used language showing a prejudice against Mr. Batista.

The spokeswoman for the appeal court said a decision on the lawyers' motion will likely be taken next week. Two of three judges on that panel have already voted to have Judge de Souza replaced, she said.

In a December interview with The Wall Street Journal, Judge de Souza denied that he acted impartially toward Mr. Batista.

A spokesperson for the appeals court couldn't say what penalties Judge de Souza might be subject to regarding his driving Mr. Batista's Porsche. But lawyers defending Mr. Batista say that constitutes administrative wrongdoing, a crime that can lead a sentence between two to 12 years.

Write to Luciana Magalhaes at Luciana.Magalhaes@dowjones.com

Access Investor Kit for Óleo e Gás Participações SA

Visit http://www.companyspotlight.com/partner?cp_code=P479&isin=BROGXPACNOR3

Access Investor Kit for Volkswagen AG

Visit http://www.companyspotlight.com/partner?cp_code=P479&isin=DE0007664005

Access Investor Kit for Volkswagen AG

Visit http://www.companyspotlight.com/partner?cp_code=P479&isin=DE0007664039

Access Investor Kit for Porsche Automobil Holding SE

Visit http://www.companyspotlight.com/partner?cp_code=P479&isin=DE000PAH0038

Access Investor Kit for Óleo e Gás Participações SA

Visit http://www.companyspotlight.com/partner?cp_code=P479&isin=US68061P1075

Access Investor Kit for Porsche Automobil Holding SE

Visit http://www.companyspotlight.com/partner?cp_code=P479&isin=US73328P1066

Access Investor Kit for Volkswagen AG

Visit http://www.companyspotlight.com/partner?cp_code=P479&isin=US9286623031

Subscribe to WSJ: http://online.wsj.com?mod=djnwires