A Whole Island Started Floating Across a Canadian Reservoir, Then It Disappeared. Facebook/Rocky Avery

A mysterious tree-covered island has appeared and subsequently vanished from a reservoir in British Columbia, Canada, leaving local residents and officials intrigued by its sudden movement.

According to TMZ on Monday, the floating landmass, estimated to cover more than 105,000 square feet, was spotted earlier this month on the Williston Reservoir, north of Mackenzie.

The reservoir, one of the world’s largest man-made lakes, was created behind the W.A.C. Bennett Dam in 1968.

The sudden appearance and movement of the roughly 9,800-square-metre landmass has raised concerns among boaters and prompted renewed attention to how debris is monitored on the reservoir, which recorded its highest water level in 14 years this summer.