The threat posed by mines in parts of the Strait of Hormuz is not fully understood, and ships should consider avoiding the area, Reuters reports, quoting a US Navy advisory.

“The status of the TSS mine threat is not fully understood. Consider avoidance of that area,” says the advisory sent by the US Navy’s US NCAGS agency to mariners and seen by Reuters.

The TSS refers to the so-called Traffic Separation Scheme, which was adopted by the UN’s shipping agency in 1968 with the agreement of countries in the region, and created a ship routing system that split sailing corridors through Iranian and Omani waters in the strait.

It is not immediately clear whether the advisory was sent before or after Iranian Foreign Minister Abbas Araghchi said the Strait of Hormuz was open following the agreement of a ceasefire in Lebanon.