The balloons interfered with 30 flights, impacting some 6,000 passengers, according to Lithuania’s National Crisis Management Center. Flights resumed at 4:50 a.m. (0150 GMT) Sunday.

While the balloons turned out to be ferrying cigarettes, Europe is on high alert after intrusions into NATO’s airspace reached an unprecedented scale last month. Some European officials described the incidents as Moscow testing NATO’s response, which raised questions about how prepared the alliance is against Russia.

Lithuania and the rest of the Baltics are especially concerned. On July 10, a drone identified as a Russian-made Gerbera flew into Lithuania from Belarus and crashed in Vilnius County.

Another crashed at a military training ground on July 28 and was found a week later. The military later said it was carrying an explosive device. After those incidents, the parliament voted to allow the armed forces to shoot down any unmanned drone violating its airspace.

18,000 packs of smuggled cigarettes were recovered

Two of the balloons flew above Vilnius Airport, according to spokesperson Darius Buta. More than two dozen reached the wider Vilnius County. The balloons were recorded flying between roughly 8:45 p.m. Saturday and 4:30 a.m. Sunday.

Border police recovered 11 balloons and some 18,000 packs of smuggled cigarettes in various locations, Buta told The Associated Press.

Vilnius, Lithuania’s capital, is located some 40 kilometers (25 miles) west of the border with Russian ally Belarus. Belarusian smugglers are increasingly using the balloons, which are much cheaper than drones, for smuggling cigarettes into the European Union, Buta said.

Similar incidents, but with fewer balloons, were reported in August. Last year, 966 hot-air balloons entering from Belarus were intercepted by Lithuanian authorities. There have been 544 recorded this year.

“Both smuggling balloons and drones are criminal activities, but not as provocations or acts of sabotage,” Buta said.