SunPower (NSDQ: SPWRA, SPWRB) might have to restate its financial results because its manufacturing operations in the Philippines appeared to have over and under reported expenses in 2008 and the first three quarters of 2009.

The San Jose, Calif.-based company said an ongoing investigation so far has determined that about $9 million worth of entries should have been included in 2008.

The company's audit committee also has spotted $1 million of overstated expenses in the cost of goods sold for the first quarter of this year. For the second quarter, $14 million of expenses in the same category were understated, the company said. The third quarter saw understated expenses of $2 million.

SunPower said it hasn't determined whether it needs to restate its financial results, but warned that its previously reported financial statements should not be considered credible anymore.

The company plans to update investors about its investigation within 30 days.