TALLINN, Estonia -- Traffic on the key bridge connecting Crimea to Russia’s mainland has been halted amid reports of explosions.

The governor of Crimea, which was annexed by Russia in 2014, announced the closure early Monday but did not specify the reason.

News reports said local residents heard explosions before dawn, but there was no confirmation.

The 19-kilometer (12-mile) bridge that was opened in 2018 is the main land connection between Russia and the Crimean peninsula.

The bridge that spans the Kerch Strait was damaged in October by a truck bomb and required months of repairs before resuming full service. The bridge carries both road and rail traffic and is an important supply artery for Russia’s war in Ukraine.