BEIJING (AP) — Authorities have lifted a monthlong pandemic lockdown on the northern Chinese city of Xi’an and its 13 million residents.

The announcement Monday followed the restart of commercial flights from the city the day before.

Xi’an has been a cornerstone of the ruling Communist Party’s “zero tolerance” strategy toward COVID-19 that mandates lockdowns, travel restrictions and mass testing whenever a case is discovered.

Xi’an is about 1,000 kilometers (600 miles) southwest of Beijing, where the Winter Olympics open Feb. 4.

Access to the city was suspended Dec. 22 following an outbreak attributed to the delta variant of the coronavirus.

Meanwhile, the 2 million residents of one Beijing district have been ordered to undergo testing following a series of infections.