(CNN) -- Senior State Department and Diplomatic Security officials may have covered up or stopped investigations of inappropriate or even criminal misconduct by staff, according to an internal memo from the department's Office of the Inspector General.

The timeline surrounding the allegations places the incidents during former Secretary of State Hillary Clinton's tenure, opening the possibility that a widening scandal might taint both her record and her possible political aspirations. Clinton has also taken heat for the department's response to the September 2012 attack on the U.S. Consulate in Benghazi, Libya.

Regarding the latest allegations, CNN was provided the documents by a lawyer for a whistle-blower who is a former senior inspector general investigator.

They include:

• An active U.S. ambassador "routinely ditched his protective security detail in order to solicit sexual favors from both prostitutes and minor children," the memo says. The ambassador's protective detail and others "were well aware of the behavior," the memo asserts. When a diplomatic security officer tried to investigate, undersecretary of state for management Patrick Kennedy allegedly ordered the investigator "not to open a formal investigation."

On Tuesday, CNN obtained a statement from the ambassador, who vigorously denied the allegations, calling them "baseless."

The memo itself, purportedly written by Ambassador Larry Dinger, describes some of the information as coming from office chatter.

"Sometimes the sources are one or more agents who became aware of the case from colleagues in what, given cubicles, can be a collegial environment," the memo says.

• A State Department security official in Beirut allegedly "engaged in sexual assaults" against foreign nationals working as embassy guards. The security official, the Office of the Inspector General says, was also accused of committing "similar assaults during assignments in Baghdad, and possibly Khartoum and Monrovia." The office's memo says that an inspector general's investigator who went to Beirut to try to conduct an investigation was not given enough time to complete the job.

• A member of Clinton's security detail allegedly "engaged prostitutes while on official trips in foreign countries." The inspector general's agent assigned to investigate "concluded" that the "prostitution problem was endemic."

• In Iraq, an "underground drug ring" may have been operating near the U.S. Embassy and "supplying" drugs to State Department security contractors, but an agent sent to investigate the allegations was prevented from completing the job.

State Department spokeswoman Jen Psaki responded to the allegations Monday.

"We hold all employees to the highest standards," she said. "We take allegations of misconduct seriously and we investigate thoroughly. All cases mentioned in the CBS report were thoroughly investigated and under investigation, and the department continues to take action."

The allegations were first reported by CBS on Monday.

Nicholas Merrill, a spokesman for Hillary Clinton, said Clinton was completely unaware of any of the investigations mentioned in the Office of the Inspector General's reports and memos, including the case involving her personal security detail allegedly soliciting prostitutes.

"We learned of it from the media and don't know anything beyond what's been reported," Merrill told CNN in a written statement.

CNN's Jill Dougherty and Elise Labott contributed to this report.