A longtime aide to disgraced financier Bernard Madoff instructed two assistants to generate trading tickets, now believed to be bogus, for Madoff's investing clients, the Wall Street Journal reports, citing to information the assistants gave the government in the investigation.

The assistants told prosecutors their supervisor, Annette Bongiorno, a four-decade veteran of the Madoff firm, would ask them to research daily share prices for blue-chip stocks from the previous month or several months, according to a person familiar with their statements, the Journal reports.

Using the data of past share prices, Bongiorno would then instruct the assistants to generate "tickets" showing purported trades, which resulted in gains that were in line with Madoff's steady annual returns, this person said. Bongiorno couldn't be reached for comment, the newspaper reports.

The development comes as Madoff signaled last week that he will plead guilty to numerous crimes during a scheduled hearing in federal court on Thursday, people familiar with the case say. Madoff's attorney, Ira Sorkin, declined to comment, the Journal says.

A person close to the case said last week that Madoff is expected to plead guilty at a hearing Thursday to charges that he carried out a massive swindle of as much as $50 billion, the Associated Press reports. A federal judge issued an order inviting potential victims who wish to be heard at Thursday's hearing to notify the court a day earlier.

Madoff is waiving his right to have a grand jury hear the government's case against him, agreeing instead to be charged directly by prosecutors, a step defendants take when they are preparing to plead guilty in a case, according to AP.

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