Unexploded bomb found near Borussia Dortmund's Westfalenstadion

Borussia Dortmund had to relocate their news conference ahead of Saturday's Revierderby after an unexploded World War II bomb was discovered near their stadium.

The 250kg bomb, discovered in the hours prior to coach Jurgen Klopp's prematch media briefing for the Schalke clash, was safely defused later in the day and the derby is to go ahead as scheduled at the Westfalenstadion.

The bomb -- known as a "Blindganger," which is also a term to describe a misguided person -- was found after analysing aerial pictures of the surroundings ahead of construction works on the VIP section of Dortmund's home ground.

Such analysis is common procedure in Germany, which was hit hard by bombs dropped by Allied and Soviet forces during the final years of World War II.

While the bomb was deactivated, the area had to be evacuated, and Klopp therefore had to meet the media at the club's training ground.

Referring to recent fan violence surrounding the Revierderby, Klopp told reporters: "I just hope that, on Saturday, there are no more Blindganger inside the stadium."

The ground below several cities in Germany remains littered with unexploded bombs from World War II and Thursday's incident was nothing out of the ordinary for a nation in which state-controlled Kampfmittelbeseitigungsdienst (KMBD) bomb disposal teams are readily available in most areas.

The city of Dortmund has witnessed mass evacuations in recent years, with 17,000 having to leave their homes when a large bomb was deactivated in 2014, while the previous year saw 20,000 people cleared from the area when a bomb was located in the city.

"There are several bombs per year," a spokesperson for the city of Dortmund, Michael Meinders, told ESPN FC.

In the North Rhine Westphalia state, 228 bombs over 50kg were detected in 2013, with 918 smaller explosives.

Hans-Peter Eser, who works for the KMBD in the Dortmund region, told ESPN FC: "This can happen for future derbies too. It's not foreseeable when all bombs will have been detected."