WASHINGTON (Reuters) – Federal regulators said yesterday they do not know the whereabouts of billionaire Texas banker Allen Stanford, charged with a “massive” US$8 billion international financial fraud.

“We are unaware of his whereabouts,” Securities and Exchange Commission spokeswoman Kimberly Garber said from Texas.

Asked if Stanford may be outside the United States, she said: “Certainly that’s a possibility, but we don’t know.”

U.S. marshals assisting the SEC have been unable to serve Stanford with court orders freezing assets and appointing a receiver to run his Stanford Financial Group companies since a raid on his Houston headquarters Tuesday, Garber said.

Garber said she was unaware of any warrants for Stanford’s arrest and said the SEC was still hoping for his voluntary cooperation on the civil fraud charges.

“Certainly he is still subject to the court orders. To that extent, we certainly want to ensure that he is served,” Garber said. She said two executive who were charged with Stanford, Laura Pendergest-Holt and Jim Davis, had been served.

The FBI is in communication with the SEC regarding the Stanford case, FBI spokeswoman Shauna Dunlap said. She gave no more details. “The FBI is certainly aware of the SEC investigation, and we have been in contact with the SEC,” Dunlap said.

The SEC said in court papers disclosed Tuesday that Stanford had failed to appear in recent weeks for testimony ordered by subpoena.

CNBC reported that he had tried to hire a private jet to fly one-way to Antigua from Houston, but the jet lessor refused to take his credit card.