U.S. Energy trader SemGroup LP spiraled into bankruptcy last year after its top executives lied about its liquidity problems and mismanaged a speculative trading strategy, according to a report released by the company's court-appointed examiner on Wednesday.

SemGroup, once the 14th-largest privately-held U.S. company and the parent of SemGroup Energy Partners LP , collapsed last year after $3.2 billion in bad bets on oil prices.

Louis Freeh, former head of the U.S. Federal Bureau of Investigation, who was appointed in October to investigate the firm's collapse said in his final report on Wednesday, that the company's former chief executive Thomas Kivisto had put the entire company at risk through speculative oil trading as oil prices rose to record highs last year.

Freeh said that Kivisto, the company's former chief financial officer Gregory Wallace, and former treasurer Brent Cooper had refused his requests for interviews, and invoked their fifth-amendment privilege against self-incrimination during the examiner's depositions.

Freeh said SemGroup's creditors could potentially bring suits against its former executives for fraud, making false statements, unjust enrichment, breach of fiduciary duty, breach of contract and corporate waste.

Creditors have previously alleged that SemGroup's trades fell outside the bounds of normal hedging activity.

The Tulsa, Oklahoma-based company is hoping to emerge from bankruptcy protection later this year as a public company after reorganizing its debt.

The case is In re SemCrude, L.P., U.S. Bankruptcy Court, District of Delaware, No. 08-11525.

(Reporting by Emily Chasan; Editing Bernard Orr)