MADRID (AP) — An Italian judge has ordered Italy to release a Spanish aid group's rescue ship that was impounded for taking 218 migrants to Italy, finding that the ship was operating in an emergency when it launched the rescue, the group said Monday.

Proactiva Open Arms said the ship was free to leave the Sicilian port of Pozzallo, but that prosecutors are still investigating whether its crew should face charges of criminal association and aiding illegal immigration.

Ragusa investigating magistrate Giovanni Giampiccolo recognized that the ship was acting under "a state of necessity" when it rescued the migrants off Libya's coast and refused Libyan coast guard commands to turn them over, Proactiva lawyer Rosa Lo Faro said.

The magistrate ruled that international standards call for those rescued at sea to be brought somewhere "safe" — and that Libya was not safe, the ANSA news agency reported.

The investigation stems from a tense high-seas standoff last month between the Open Arms crew and the Libyan coast guard. The group refused to hand over the migrants they had picked up in international waters and took them to Italy, where the ship was immediately impounded.

"At all times, we acted according to existing international norms and laws created to protect human lives at sea and the rights of those rescued," Open Arms said.

Amid a surge in anti-immigrant sentiment across Europe, Italy has been working to stem the tide of migrants leaving lawless Libya and arriving in Italy. It has helped the Libyan coast guard beef up its patrols, reduced the number of aid groups performing sea rescues and — in a move criticized by some aid groups — negotiated deals with Libyan militias that had long profited from trafficking humans.

The strategy has resulted in a 75 percent drop in the number of migrants arriving in Italy in the first three months of 2018, to some 6,100, according to Interior Ministry figures.