MILAN (AP) — Italian authorities have evacuated 4,000 people from the center of the northern city of Bolzano to defuse a World War II bomb found during construction.

The news agency ANSA said the bomb was defused during a three-hour operation Sunday morning. An alarm signaled the all-clear to reopen the city center, as well as a nearby north-south highway and a rail line connecting Italy with Austria and Germany.

The Neue Suedtiroler Tageszeitung identified the ordnance as an aerial bomb.

According to historian Ettore Frangipane, Bolzano, in the northern Alto-Adige region bordering Austria, suffered 13 major World War II bombing raids that damaged 60% of the city and killed 200 people.

Alto Adige was part of a broad swath of northern Italy that remained under Nazi-occupation long after Italy's 1943 Allied surrender.