PHOENIX -- The FBI has launched an investigation into the disappearance of former Detroit Pistons center Bison Dele and his girlfriend during a boating trip in the Pacific Ocean.

Dele, girlfriend Serena Karlan and boat captain Bertrand Saldo have been missing for two months, said Andrew Black, spokesman for the FBI's San Francisco office.

Dele, formerly known as Brian Williams, played on the Chicago Bulls' championship team in 1996-97. He later signed with the Pistons, where he played for two seasons before retiring. He played at the University of Arizona in 1990 and 1991.

Dele's 57-foot sail boat was scheduled to sail from Moorea, Tahiti, to Honolulu and was last reported near Tahiti. The Coast Guard is searching for the boat.

"We are interviewing people that may have information which will explain why they disappeared,'' Black said.

Missing persons complaints were made in Colorado and Michigan, where Dele had business contacts.

Even though relatives said earlier that another two crew members were aboard the boat, the FBI said only one crew member was reported missing.

Authorities are in the process of locating Williams' older brother Kevin, also known as Miles Dabord, who lives in the San Francisco area.

Kevin Williams was questioned by Phoenix police last week in an identity theft investigation, said Karlan's stepfather, Scott Ohlgren.

Authorities would not identify the man questioned in the investigation but said he claimed to be Brian Williams.

Family members say Kevin Williams was questioned by Phoenix police last week after he allegedly tried to buy about $150,000 in gold coins while posing as his brother. He has not been seen since, but his mother, Patricia Phillips, told the Chicago Tribune she had received anguished calls from him Tuesday and Wednesday.

In those calls, Phillips told the Tribune, "(Kevin) said, 'Mom, I just need you to believe me. I wouldn't hurt my brother. I need to know that you love me before I die. I can't go to prison. You know my personality is the type that I can't survive in prison. Nobody will believe my story.' "

Phillips said authorities told her the FBI believes Kevin Williams had fled to Mexico. The FBI declined to say whether Williams, 35, was a suspect in Dele's disappearance.

Information from The Associated Press was used in this report.