The U.S. Secret Service is assisting in the investigation of a head-on car collision early Sunday morning on Interstate 66 in Northern Virginia, the agency confirmed.

The crash, which occurred just before 5 a.m., forced the closure of an eastbound portion of the highway in Arlington for about an hour, police said. It also sparked a manhunt after one of the drivers fled the scene on foot, the agency said in a statement.

As of 9 a.m., that driver remains at large, despite a search effort that included a helicopter, authorities said.

The Secret Service said one of its officers first spotted a car traveling in the wrong direction on I Street NW in Washington at 4:35 a.m. Sunday. The officer then tried to stop the wrong-way driver, but the car continued onto I-66 — traveling westbound in the eastbound lanes, the agency said.

A little later, the car crashed head-on into another vehicle, and the wrong-way driver fled the scene on foot, according to the Secret Service.

A passenger in the car that had been going the wrong way was taken into custody, then transferred to the hospital with non-life-threatening injuries, authorities said.

“It remains an ongoing investigation whether or not any charges will be sought for the passenger,” Arlington County police spokeswoman Kirby Clark said.

The driver of the vehicle that had been going in the right direction also was taken to a hospital with injuries that were not life-threatening.

According to Fox 5 DC News, one of the drivers in the crash was a “White House military pass holder.”

A Secret Service spokesman said the agency was simply providing mutual aid to local police agencies. The Arlington County Police Department is leading the investigation.

Images of the crash scene from local reporters showed a dark sedan — badly damaged on its front and right side — straddling the low concrete wall of the highway’s median. Nearby was a red sedan stopped across three eastbound lanes on the highway, as well as multiple police officers.