HONOLULU — The FBI arrested a Honolulu Police Department officer Wednesday in connection with an ongoing federal corruption investigation into the former Honolulu police chief.

Officer Derek Hahn, 46, was arrested without incident, FBI Special Agent Arnold Laanui said. Hahn made an initial appearance in federal court in Honolulu Wednesday and was released on signature bond. A preliminary hearing was set for October 31.

The arrest comes days after another Honolulu police officer and a retired major were arrested by the FBI as part of a federal corruption investigation that stemmed from a peculiar case of a mailbox former police chief Louis Kealoha said was stolen from his home by his wife’s uncle.

The FBI said in its criminal complaint that Hahn conspired to give false testimony and evidence in the mailbox case, then he and others conspired to obstruct the federal investigation into their actions.

Kealoha agreed to retire after receiving notice of the FBI’s investigation.

Hahn is part of the department’s Criminal Investigations Division, but was formerly with the Criminal Intelligence Unit, the FBI said in a statement.

“The FBI is conducting a thorough investigation into allegations of public corruption and will exert every legal effort to ensure those responsible are investigated and prosecuted,” said FBI Special Agent in Charge Paul Delacourt in a statement. “In order to restore the public’s trust in its law enforcement, we are required to root out all responsible parties.”

Hahn’s defense attorney Birney Bervar said that his client should not have been arrested and that the federal government is trying to intimidate his client.

“The fact that he was arrested today instead summonsed is an example of the intimidation and bullying by the government that has marked this investigation in the government’s attempt to get people to say what the government wants them to say,” Bervar said. “My client is not going to be intimidated, he’s going to tell the truth and the truth is there was no criminal conspiracy.”