A World War II bomb that was found in Great Yarmouth, England exploded on Friday in what authorities are calling an "unplanned" detonation.

Officials first became aware of the 250 kilogram (about 550 pounds) explosive on Tuesday, Feb. 7, when a contractor who was doing dredging work in the River Yare discovered it, according to a news release from the city. Emergency services and local authorities declared a "major incident" and activated emergency plans. An Explosion Ordnance Device team was also summoned to the area. Roads were closed and the immediate area was evacuated. 

On Friday, work began to disarm the explosives remaining in the device, but somehow it detonated, causing a large explosion that was captured on video by a police drone. The video was shared on Twitter. 

In a news release, officials said that a protective sandbox had been built around the bomb in case of an unexpected detonation. That sandbox prevented injuries, and on Twitter, officials said that "no one was injured" in the day's events. 

Evacuation orders have been lifted and Great Yarmouth Borough Council Chief Executive Sheila Oxtoby thanked community members for their patience and understanding throughout the multi-day process. 

"This has been an unsettling time for many people, most of all for those who were evacuated from their homes. Safety of the public has been at the heart of decision making throughout this multi-agency operation. While it may have been slow, yesterday afternoon's events show why it was so important to take all necessary measures to minimize any risk to the public," Oxtoby said, according to the news release. "... I'd like to thank everyone involved for bringing this to a safe conclusion and we will continue to help those residents displaced." 

It's not clear how many people were displaced due to the explosion. 

Officials said that a nearby tower crane seen in the drone video has been deemed "safe." Environment Agency engineers will inspect a river wall today that was damaged in the explosion, but "initial assessments show" that the flood defense it provides has not been compromised.