THESSALONIKI, Greece — A line of cars roughly about 5 kilometers (3 miles) long formed on Monday morning at Bulgaria’s main border crossing with Greece, after Greece reopened its border to tourists.

Greece had announced it was reopening to visitors Monday, leading many to believe the border crossing would be open at midnight Sunday to Monday. Instead, the Promahonas crossing was due to reopen at noon, leading to a long backup of waiting cars.

Officials opened the border nearly an hour earlier due to the waiting travelers, and the line was easing shortly after midday, authorities said. Health officials were conducting randomized coronavirus tests on those entering, with roughly one person in every 15 checked.

Greece’s border with North Macedonia remains closed to tourists and is only open to those for travel deemed essential, leaving the Bulgarian crossing as the only convenient alternative for tourists from the Balkans to drive into Greece.

The country’s two main airports — one in Athens and one in the northern city of Thessaloniki — also reopened to tourists Monday, while international flights to regional airports will restart on July 1.