(CNN) -- Two Secret Service supervisors on President Barack Obama's protective detail are under investigation for alleged misconduct, a federal law enforcement source with knowledge of the internal Secret Service investigation told CNN's John King.
The details were first reported in the Washington Post Wednesday night.
The investigation began after an incident at the posh Hay-Adams Hotel near the White House in May. As first reported by the Post, one Secret Service agent allegedly removed ammunition from his service weapon and left a bullet in the room of a female guest, whom he had met in the hotel bar.
The agent tried to regain entry to the room when he realized the bullet was left behind, the Post said. Hotel staff notified the White House after he identified himself as a Secret Service agent and demanded to be let in to the room.
No police report was filed and no complaint was filed with the Secret Service by any of the parties involved, a government source told CNN's Joe Johns Thursday.
"The Secret Service takes allegations of improper behavior seriously and works diligently to investigate and resolve issues. Any misconduct is regrettable, but when it is identified, appropriate action is always taken based on established rules and regulations," Edwin M. Donovan, deputy assistant director of the Secret Service, said in a statement.
The internal investigation was launched as a result of inquiries by the Post, the government source said.
That probe led to a routine search of the agent's agency-issued BlackBerry, the Post reported.
The federal law enforcement source confirmed that the agent, a supervisor, and a second supervisor were discovered to have sent sexually suggestive e-mails to a female Secret Service employee. Nothing explicitly suggestive has been found, the government source said.
The first supervisor was removed from his position, the source said, but the second supervisor remains on the presidential security detail. The Post reported that the second supervisor was removed from the security detail.
While the paper named the two supervisors involved, CNN is not yet identifying them.
The investigation follows the Secret Service scandal in April 2012 involving prostitution and drinking before a presidential trip to Cartagena, Colombia. A review prompted new rules of conduct for Secret Service employees in the wake of the incident.
Sen. Ron Johnson said at a Senate hearing Thursday that despite assurances from Department of Homeland Security and Secret Service that the 2012 Cartagena prostitution scandal involving presidential detail agents was an anomaly, congress has found similar instances in 17 countries.
"Yesterday we learned that two senior level United States Secret Service agents assigned to the President's detail were recently disciplined for sexual misconduct. According to whistle-blowers, one of these men helped lead the USSS internal investigation of the sexual misconduct in Cartagena in April of last year. This is like the fox guarding the hen house," the Wisconsin Republican said. "This type of behavior jeopardizes the security of the President of the United States and makes U.S. government personnel susceptible to coercion and blackmail."
While not addressing the specifics of the most recent case, William Hillsburg, acting director of the Public Affairs Department of the Homeland Security office of the inspector general, said that in the next couple of weeks his office is expected to release an inspection report with an in-depth look at the culture of the U.S. Secret Service.
The report will look at whether there's something in the Secret Service culture that led to the behavior in Cartagena. It will also include recommendations on how agents are trained.