Six people were taken to hospital on Saturday night following a crash near St. Johnston.
Gardaí confirmed that all six were involved in a two-car collision that occurred at around 8.45pm.
Their injuries, the garda source added, varied from minor to serious and were not thought to be life-threatening.
The road remained closed until around 12.30am.
Gardaí in Letterkenny are investigating. They ask anyone who may have witnessed the collision, or who might have information relevant to their investigation, to contact them on 074 916 7111.
According to a Porthall resident, who asked not to be named, a number of local people, as well as people not from the area, were among those injured.
“It was a very serious crash: the cars were badly damaged,” the local said. “There were a lot of emergency crews here from both sides of the border - gardaí, fire brigade and ambulances.
“We’re all very relieved to hear that those who were taken to hospital will be okay.
The crash, which took place at the humpbacked bridge on the border between Porthall and Carrickmore, was the second to happen at Porthall on Saturday night.
Just one hour earlier, at around 7.45pm and only a mile or so away, and single vehicle was also involved in a collision. A local resident said the driver involved in this incident escaped unharmed.