Italian officials say rough seas have increased movements of the crippled Costa Concordia and are thwarting the start of fuel removal a month after the cruise ship capsized off a Tuscan island.

The national office overseeing search and anti-pollution operations said Friday that instruments registered increased and faster movements of the ship, which is resting on its side just outside Giglio island's port. But they said the movements have since slowed down. If the ship keeps shifting, it could drop down onto deeper seabed, complicating plans to remove fuel.

At least 17 people died in the incident and 15 are missing. Italian TG5 broadcast video showing confusion among the captain and crew on the ship's bridge in the hour after Concordia rammed a reef.