Two U.S. admirals — including the director of naval intelligence — are under investigation as part of a major bribery scandal involving a foreign defense contractor, Navy officials announced Friday night.

Vice Adm. Ted “Twig” Branch, the service’s top intelligence officer, and Rear Adm. Bruce F. Loveless, the Navy’s director of intelligence operations, were placed on leave Friday, and their access to classified material was suspended, the Navy said in a statement.

Both admirals are being investigated for their ties to a Singapore-based defense contractor, Glenn Defense Marine Asia, whose chief executive was arrested in September on charges that he bribed other Navy officers into giving him classified or privileged information in exchange for prostitutes and cash.

Two Navy commanders and a senior Naval Criminal Investigative Service agent have already been arrested, and a captain was relieved of his ship’s command last month in connection with the case.

But the announcement that two admirals in charge of protecting the Navy’s secrets have been swept up in the investigation makes the crisis the worst to tar the Navy since the 1991 Tailhook scandal, when a convention of naval aviators sexually assaulted scores of women.

Navy officials said they were bracing for even more bad news to emerge from a corruption case that has expanded swiftly since it became public in September. “We do believe that other naval officers will likely be implicated in this scandal,” Rear Adm. John F. Kirby, the Navy’s chief spokesman, said in a telephone interview.

The Navy did not disclose why Loveless and Branch had drawn the scrutiny of investigators but said their alleged misconduct occurred prior to their current assignments and before they became admirals.

“There is no indication, nor do the allegations suggest, that in either case there was any breach of classified information,” Kirby said in a statement.

But a Navy official who spoke on the condition of anonymity because of the sensitivity of the case said the NCIS recently uncovered evidence of “personal misconduct” against Branch and Loveless as the investigation into Glenn Defense Marine widened.

Neither Branch nor Loveless has been charged with a crime or service violation, and both men retain their rank while the investigation proceeds, the Navy said. The decision to suspend their access to classified information was made by Navy Secretary Ray Mabus.

The suspension of two senior intelligence officials raises serious questions about whether national security may have been compromised because of improper contact between Navy officers and Glenn Defense Marine.

Prosecutors from the U.S. attorney’s office in San Diego have charged the two Navy commanders with passing classified information about ship and submarine movements to Leonard Glenn Francis, a Malaysian national and the chief executive of Glenn Defense Marine.

Navy contracting officials raised suspicions about Francis — who is known as “Fat Leonard” in Navy circles because of his imposing girth — as far back as 2005. But prosecutors allege he was able to dodge scrutiny by bribing Navy officers and the NCIS agent for inside information about law enforcement probes and contract audits.