World War II bomb in Greece
Military officers unload sacks of sand next to a hole in the ground (right), where a World War II bomb was found during excavation works at a gas station, before an operation to defuse it in Thessaloniki, Greece, Feb. 10, 2017. REUTERS/Alexandros Avramidis

A World War II-era bomb is set to be defused Sunday in the northern Greek city of Thessaloniki after authorities evacuated over 70,000 people from the area, according to reports. The nearly 550-pound bomb was discovered during an excavation work at a local gas station last week.

Local officials said the entire process of evacuating the city and defusing the bomb is likely to take about eight hours. And the evacuation is “obligatory,” according to regional security chief Apostolos Tzitzikostas.

Local military spokesman Col. Nikos Phanios said he is more cautious about the entire process.

“We don’t know what we’re going to find,” Phanios told Agence France-Presse (AFP). Defusing the explosive and shifting it to a military shooting range “could take us up to two days,” he added.

Phanios also said that it remains unclear which side in the World War II dropped the bomb or when it fell, AFP reported.

The evacuation began early Saturday. Buses were reported to have carried residents living within a 1.2-mile radius of the bomb defusing site to local gyms, stadiums and cafes, police said, according to Reuters. The news agency added that this is Greece’s biggest peacetime evacuation.

People staying in Thessaloniki reportedly faced problems with bus and train networks. According to AFP, facilities were set up to shelter evacuees. Over 300 disabled people and bed-ridden patients were reported to have been first evacuated Saturday with the help of 20 ambulances, officials in Thessaloniki said.

Those living in a nearby refugee camp will also have to be evacuated, the migration ministry reportedly said. It is not clear how many refugees would be affected.