OAKLAND -- Port of Oakland executive director Omar Benjamin said Monday that he would "retire" effective immediately, even as the investigation into his involvement in a strip club expense reimbursement continued.

The port chief was found to be part of a group whose $4,537 tab at a Texas strip club was paid for by the Port of Oakland, according to newly released expense records.

The Port of Oakland released the full version of the expense records Friday as scrutiny over the spending continued. The records showed for the first time that Benjamin helped run up the strip club tab that was passed off as a normal business meeting.

Benjamin and the port's maritime director, James Kwon, were said to be subject to dismissal if the investigation found they improperly billed the port, according to the agency's administrative policies. Kwon remains on administrative leave.

"I am cooperating with the port inquiry and will do whatever I can to resolve this matter constructively and in the interests of the Port of Oakland," Benjamin said last week by email.

Port policy allows "reasonable and necessary travel, entertainment and other expenditures incurred in the course of conducting the business of the port." It does not say where port employees can be entertained or how much executives can spend entertaining them.

Aviation director Deborah Ale Flint will continue to serve as acting executive director; she was put in charge of port operations after Benjamin was placed on leave Oct. 18.

Staff writer Angela Woodall contributed to this report.