ROME (AP) — An Italian prosecutor says he is investigating employees of aid groups that are rescuing migrants off Libya for allegedly facilitating illegal migration, but says it’s not a punishable crime since saving lives at sea is paramount.

Trapani Prosecutor Ambrogio Cartosio stressed Wednesday that he wasn’t investigating the aid groups themselves, but rather individuals who work for them.

His testimony to the Senate’s defense committe was the latest from law enforcement about alleged contacts between aid groups and Libyan traffickers who send overcrowded boats full of migrants to Italy. The groups have denied they’re in cahoots with the traffickers and have blasted prosecutors for spreading rumors without providing proof.

Cartosio also said migrants arriving in Trapani have reported that Libyan coast guard officials — recently entrusted with Italian patrol boats and know-how to try to stem the migrant flows — have instead demanded bribes to let the boats continue their journeys north.