WASHINGTON -- Outside law enforcement experts are looking into how the State Department investigates allegations of sexual crimes and other serious misconduct by diplomats amid charges that senior officials have improperly halted such probes.

The department said Tuesday that its internal watchdog, the Office of the Inspector General, had contracted with former law enforcement agents to review the process and determine whether investigators in the Bureau of Diplomatic Security have the independence necessary to do their jobs effectively.

Officials said the review is expected to be complete later this summer.

The review was ordered after at least one investigator complained that probes into several cases, including allegations of diplomats soliciting prostitutes, had been quashed by higher-ups for political or other reasons.

The State Department denied that any allegations of questionable or illegal behavior by diplomats have been covered up and said that any proven wrongdoing is punished.

"We hold all employees to the highest standards," spokeswoman Jen Psaki said after CBS News reported details of an internal department memo listing eight cases in which probes had been allegedly curtailed improperly.

The outside review of the investigative process was ordered after a February report from the inspector general found that Diplomatic Security's Special Investigations Division -- which looks into allegations of substance abuse, domestic violence, firearms violations, sex crimes and other serious misconduct -- suffered from the perception of a lack of independence.

The chairman of the House Foreign Affairs Committee, Rep. Ed Royce (R-Calif.) said he was "appalled" by both the allegations of misconduct and the "reported interference in the investigations."

"The notion that any or all of the cases contained in news reports would not be investigated thoroughly by the department is unthinkable," said Royce.

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