(photo by Mass Communication Specialist 3rd Class Jonah Stepanik)

What appeared to be a contact-style naval mine was detected mysteriously floating off the coast of Washington state Aug. 28, 2018, prompting the US Navy to send in a team to destroy it, according to local reports.

Images of the mine, which was first discovered by the Washington State Department of Natural Resources, showed a round, rust-covered object with rods protruding from it floating in the water near Bainbridge Island, located across the way from Seattle and near Naval Base Kitsap, which is home to one of the Navy's most important shipyards, Puget Sound.


The Navy sent an Explosive Ordinance Disposal team to deal with the mine while the Coast Guard and local authorities set up a safety zone, encouraging nearby residents to shelter in their homes.

"Upon initial inspection, the unidentified moored mine was found to have decades of marine growth," the Navy revealed. After lassoing the mine and dragging it out to open waters, the Navy EOD team detonated the mine at around 8 pm Aug. 28, 2018.

The Navy noted that because there was no secondary explosion, the old mine was most likely inert, according to local media. The Navy detonated the mine at sea because it was initially unclear whether or not there were explosives inside.

Exactly how the mine ended up off the coast of Washington remains a mystery.

Featured image: Explosive Ordnance Disposal Mobile Unit 2, assigned to Commander, Task Group 56.1, conducts floating mine response training with the Kuwait Naval Force, Nov. 9, 2014.

This article originally appeared on Business Insider. Follow @BusinessInsider on Twitter.