And a United States Treasury Department investigation made public in March uncovered a money laundering ring that had moved $4.2 billion out of Venezuela though import-related schemes and other means. The investigators determined that at least $50 million had passed through the American financial system.

Mr. Maduro, a leftist president who was elected by a narrow margin in 2013, has often come under pressure to attack government corruption.

In December 2013, Mr. Maduro appointed the commission to investigate the import ploys, calling them “a fraud against the republic.”

“I am going to reveal to the country the truth about what happened there, because it was a vulgarity,” Mr. Maduro said.

Jesús Faría, a member of the commission and a governing party lawmaker, said in a television interview last month that in just a sampling of cases, the commission had found that more than 250 companies “had broken the law and that the prosecutor’s office had hundreds of companies to evaluate and investigate.”

“Nevertheless, I have not seen that any of these companies have been punished,” he added.

There appears to be only one criminal case in which prosecutors have charged a high-level official at the currency control agency with wrongdoing.

The official, Francisco Navas, was arrested in 2013 and has yet to stand trial. He is charged with money laundering and conspiracy, accused of taking bribes to sign off on millions of dollars of payments to companies for bogus imports. According to the testimony of an agency vice president, Mr. Navas charged companies the equivalent of about 46 cents for each dollar he approved.

His lawyer, Alonso Medina, said that Mr. Navas was a scapegoat, charged so that the authorities had someone to “hold responsible before public opinion.”