NEW YORK (CNN/Money) - Adelphia Communications Corp. inflated its cable-TV subscriber base by 400,000-500,000, or 10 percent, of the firm's total customer base, a newspaper reported Friday.

Additionally, investigators have turned up evidence that Adelphia kept two sets of accounting books for its capital expenditures, one of which it showed to Wall Street and boosted the amount it spent to upgrade its cable systems, the Wall Street Journal reported.

The revelations come amid bankruptcy speculation and an investigation of the nation's fifth largest cable-TV provider by the Securities and Exchange Commission over off-balance sheet transactions involving loans made to the Rigas family, which founded and controlled the company. Adelphia is also under criminal investigation by two federal grand juries, in Pennsylvania and New York.

Friday's disclosures suggest Adelphia's questionable accounting practices run far deeper than initially thought and will likely raise new questions about the company's core business.

Both the SEC and federal prosecutors are probing the subscriber numbers, a key gauge for investors of the company's strength, and the capital spending issue, the paper reported.

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Regulators are also focusing on how much Adelphia's auditor, Deloitte & Touche, knew of the off-balance sheet transactions, co-borrowing arrangements and subscriber inflation, and whether they failed to disclose that knowledge to the board, according to the report.

Deloitte said in a statement that it believes "our work for Adelphia complies with all applicable professional standards and we are confident that a final review of the matter will demonstrate this to be the case."

Adelphia is trying to raise cash and come up with options as a June 15 deadline draws closer on more than $50 million in interest expense it owes to bondholders.

Though investigators have known for weeks that Adelphia apparently inflated its subscriber numbers, early estimates were much lower than the numbers reported Friday.

Shares of Coudersport, Pa.-based Adelphia (ADLAE: Research, Estimates) are trading under $1