Prosecutors specializing in government corruption cases are leading the investigation into what authorities say was a prostitution service that charged up to $5,500 an hour — suggesting that the U.S. attorney’s office in Manhattan may have evidence that a public official hired a prostitute.

Federal prosecutors here recently unsealed a criminal complaint charging four people with running Emperors Club VIP, which advertised itself as an escort service. Prosecutors say the Emperors Club employed more than 50 high-end prostitutes.

RELATED: The Emperors Club Complaint (pdf)

During a court hearing in the case, at which the four people were arraigned, it emerged that all three of the assistant U.S. attorneys assigned to the prosecution are part of the U.S. attorney’s public corruption unit. One is the bureau’s chief, Boyd Johnson III. The unit investigates wrongdoing by both elected and nonelected officials and bureaucrats at various levels of government.

A spokeswoman for the U.S. attorney’s office in Manhattan, Yusill Scribner, would not comment when asked whether a public official was among the clients of the Emperors Club. But the involvement of the public corruption unit raised eyebrows among the defense lawyers.

“When we first got the case, we were surprised that these were the assistants handling the case,” said a defense attorney, David Gordon, who represents one of two women alleged to have booked engagements for prostitutes.

Emperors Club billed itself as a service for wealthy men that provided introductions to models as well as investment advice, according to its Web site, which has been taken down. The business generated more than a million dollars in revenue, prosecutors say, and $600,000 in cash was found at the New Jersey apartment where the two main managers of Emperors Club, Mark Brener, 62, and Cecil Suwal, 23, lived.

During the investigation, law enforcement sources intercepted more than 5,000 phone calls and text messages and accessed about 6,000 e-mails, the criminal complaint said. The complaint makes no mention of a client list.

“Rumors are feeding rumors and I have no knowledge of anybody’s little black book, assuming this is even a prostitution case,” Ms. Suwal’s defense lawyer, Daniel Parker, said. “Even if a black book existed, it’s possible that it never ever surfaces.”

If such a black book does exist it could give rise to a scandal of the sort Washington was treated to last year, when an accused madam, Deborah Palfrey, made public the phone records connected to her escort service. A senator, David Vitter, a Republican of Louisiana, apologized for “a serious sin in my past” after his number was among those released.

Federal prosecutors do not generally go after the men who hire prostitutes, even though, in some instances, cases could be made for conspiring to violate the Mann Act, a 1910 law that forbids transporting prostitutes across state lines and was also known as the “White-slave traffic act.”

If all prosecutors find is that a public official hired a prostitute, “they’re going to take a pass, and they’re not going to try to expose him,” said one former federal prosecutor in New York who spoke on condition of anonymity.

But lawyers said prosecutors might use that information to search for other illegal conduct.

“If a public official is making $112,000 a year and he is spending $3,500 a night on a call girl, you’re going to ask some questions,” a prominent defense attorney who is not connected to the case, Edward Hayes, said, adding that the “feds are in desperate straits if they’re making call girl cases.”

“If there are public officials involved, prosecutors will focus on that like a laser beam to see if there is anything else going on,” the former federal prosecutor said. For instance, prosecutors could subpoena records connected to a credit card used to hire a prostitute to see if any expenditures involved misuse of state money or campaign funds.