The two Secret Service agents who were drinking on the night they drove into a crime scene investigation near the White House almost ran over a “suspicious package,” sources told Fox News on Thursday.

The details of the March 4 incident come as officials seek to downplay what’s been the latest embarrassing episode for the troubled agency.

Police were examining the package around 10 p.m. when the two senior agents – one of whom is a top member of President Obama’s protective detail – arrived at a guard shack checkpoint that had been vacated due to its proximity to the package, which turned out to be a book covered in a shirt. 

But when the agents – identified as Mark Connolly, the second-in-command on Obama’s detail, and George Ogilvie, a senior supervisor in the Washington field office – realized the guard shack was unoccupied, the government car backed up a few feet and “nudged” an orange, four-foot-tall traffic barrel that had been placed in the roadway, sources said.

The sources said the car did not appear to be out of control or traveling at a high rate of speed, and when the barrel was struck by the car, it did not tip over or cause damage to the vehicle. They nearly ran over the package that was being examined, although they did not run over it.

The incident, which happened during a steady downpour, was over in less than 30 seconds.

The Washington Post has reported that the officers on duty who witnessed the incident wanted to arrest the agents and conduct sobriety tests, but they were ordered by a supervisor on duty that night to let the agents go home. One source told Fox News they could smell alcohol on the agents, and said it was well-known that Secret Service agents had been attending the retirement party of spokesman Ed Donovan earlier that night.

Another source told Fox News that Secret Service Director Joseph P. Clancy wasn’t notified immediately because the incident wasn’t initially seen as a problem, but that he and Department of Homeland Security Secretary Jeh Johnson were notified the next day.

A spokesman with the Department of Homeland Security inspector general's office told Fox News on Thursday that they are now investigating the incident, after it was referred by the Secret Service. 

"We cannot discuss details of our ongoing investigation," the spokesman said. 

Obama was informed of the incident earlier this week, but has “full confidence” in Clancy, who took over the agency in February, White House Deputy Press Secretary Eric Schultz said Thursday.

But reaction on Capitol Hill has ranged from outraged to incredulous.

“These embarrassing incidents have a profoundly negative effect on the reputation and motivation of thousands of hard-working Secret Service members who have committed their careers to protecting the president,” Sen. Ron Johnson, R-Wis., said in a statement Thursday. “A few bad apples are forcing the Secret Service to account for itself in the media and distracting it from a mission in which it must not fail.  This is not acceptable.”

“The bottom line is the Secret Service has to get overhauled,” Sen. Chuck Schumer, D-N.Y., said. “What happened the other day shows the overhaul has long a way to go.”

The incident is the latest in a series of embarrassing episodes for the Secret Service, which have raised questions about the agency's leadership and ability to protect the president.

In September, a man with a knife climbed over the White House fence, sprinted to the mansion's front door and made it to the East Room. The incident led to the resignation of the agency's director, Julia Pierson. Six months before, several agents were implicated in tales of heavy drinking, one of which took place ahead of a presidential visit to the Netherlands and the other after a late-night traffic accident in Miami.

In the spring of 2012, some agents and U.S. military personnel who were preparing for a presidential trip to Cartagena, Colombia, for the Summit of the Americas hired local prostitutes and brought them back to their hotel rooms.

A total of 13 of Secret Service officials were implicated. Three employees returned to duty, six either resigned or retired and four had their clearances revoked and were removed, according to an inspector general report.

Clancy is scheduled to appear before the House Homeland Security Appropriations Subcommittee. The routine meeting is intended to discuss fiscal matters, but a senior congressional source told Fox News on Thursday that the director would be questioned about the barricades incident.

“He is in for a hell of a grilling,” the source said.

Fox News’ Chad Pergram contributed to this report.