NEW YORK (CNN/Money) - The Securities and Exchange Commission is once again looking into the way Tyco International accounted for its many acquisitions, a person familiar with the matter said.

The inquiry is not a formal investigation into Tyco (TYC: down $0.35 to $11.05, Research, Estimates), whose billions of dollars in acquisitions through 2001 helped profits jump five-fold over the last five years.

But while investors have worried that Tyco's complex accounting masks Enron-style problems, the diversified manufacturer has not restated profits. In February, it warned that full-year earnings forecasts may fall short.

Word of the SEC inquiry comes a week after former Tyco CEO Dennis Kozlowski pled not guilty to sales tax evasion charges. Kozlowski resigned a day before the indictment.

The SEC declined to comment on word of the investigation, as did Tyco.

"If we had a material event involving an investigation by the SEC, we would disclose it," a Tyco spokesman told Reuters.

Tyco, which reported profits of 14 cents per share in 1996, said profits rose to 72 cents a share last year, a period when Tyco reported $36.3 billion in sales. Its shares are down more than 80 percent this year, shaving $92 billion from the company's market value.

The SEC as early as 1999 was looking into the handling of acquisitions by Tyco. But the federal agency took no action.

The collapse of Enron, which went bankrupt in December after restating profits, have caused investors to question former high-flying companies with complicated bookkeeping.