Two United States Secret Service agents who drove a government vehicle within a few feet of a suspicious package near the White House were "more likely than not...impaired by alcohol," a government report to be released Thursday concludes.

One of the agents involved plans to retire in the wake of the investigation, multiple sources confirm to CBS News.

The report, prepared by Inspector General for the Department of Homeland Security John Roth, says the agents, Marc Connolly and George Ogilvie, "displayed poor judgment and a lack of situational awareness" when they drove through an active investigation after attending a party for a retiring colleague on the evening of March 4th.

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Connolly, a 27-year veteran of the service and the number two in President Obama's protective detail, has told colleagues he will retire. Ogilvie serves as the assistant to the special agent in the Washington field office. Both have been placed on paid leave.

"I am disappointed and disturbed at the apparent lack of judgment described in this report. Behavior of the type described in the report is unacceptable and will not be tolerated," said Secret Service director Joseph Clancy.

The party began at 5:30 PM at Fado Irish Pub in downtown Washington, the report says. Ogilvie and Connolly left the bar at 10:45 PM. According to an interview with the inspector general, Ogilvie said he consumed two scotches and part of one beer. Connolly said he drank two beers.

Around 10:45, the agents got into Ogilvie's government-issued SUV and headed for the White House complex to retrieve Connolly's vehicle parked there. Twenty minutes earlier, a suspicious package had been reported at the E St. entrance of the White House.

The agents proceeded through an initial checkpoint to a driveway at 15th St and E St. where a "series of bike rack-type barriers and a lightweight orange plastic barrel" had been set up, according to the report. Ogilvie used the bumper of his vehicle to nudge the construction barrel roughly five feet in order to reach a secondary checkpoint.

In the process, the SUV came within a few feet of the suspicious package, a screengrab of surveillance video reveals.

Three uniformed division officers inspected the vehicle and reported that they did not smell alcohol, but called a supervisor to say the agents were "not making sense," the report says.

The supervisor, a uniform division watch commander, arrived on the scene and detected the "slight odor of alcohol" emanating from the car, but judged Ogilvie, the driver, to be "polite and professional." The watch commander described Connolly as "having a flushed face [and] glazed eyes."

The watch commander believed Connolly was intoxicated, but assessed Ogilvie "fit to drive." Both agents were allowed to leave without a sobriety test and drove home in their respective vehicles, the inspector general says.

Inspector General Roth's report suggests the watch commander erred in not administering a field sobriety test, but says "the watch commander's actions must be considered in light of the vast disparity in rank between the watch commander and Connolly," a senior member of the service.

Secret Service policy on drinking and operating a government vehicle was somewhat vague prior to the incident. It has since been clarified to conform with Department of Homeland Security guidelines. No employee may operate a government-owned vehicle within 8 hours of consuming alcohol.

Connolly and Ogilvie did not report the incident to their superiors. Connolly believed it was a "misunderstanding," the report says. Director Clancy did not find out about it until March 9th, 5 days later.