MADRID — A Sicily prosecutor has opened a preliminary investigation into allegations a U.S. Navy vessel, the expeditionary fast transport ship Trenton, delayed rescuing migrants from a sinking dinghy from which some 76 people drowned in June.

The June 12 rescue off Libya came at a tense time on the Mediterranean, with Italy’s new populist government refusing to let aid groups dock in a bid to dissuade them from rescuing migrants.

The Trenton did rescue 41 people. But a half-dozen survivors told La Repubblica newspaper that the ship delayed intervening until after their dinghy started sinking, over an hour after the migrants first spotted the U.S. flags on the ship.

Ragusa Prosecutor Fabio D'Anna confirmed Tuesday he had opened an investigation into their claims.

The U.S. Navy's 6th Fleet didn't immediately comment.

A life vest lies on the rocks near the village of Canos de Meca in southern Spain onTuesday. Spain's maritime rescue service says at least 17 people have died trying to reach Spanish territory in boats departing from North Africa but rescued 80 people Monday from two boats and recovered the bodies of 13 dead migrants in the Alboran Sea, part of the western Mediterranean route into Europe. In a separate incident, the Spanish Civil Guard says it found four bodies of migrants and 22 survivors, all men from northern Africa, after their wooden dinghy hit a reef. (Javier Fergo/AP)
A life vest lies on the rocks near the village of Canos de Meca in southern Spain onTuesday. Spain's maritime rescue service says at least 17 people have died trying to reach Spanish territory in boats departing from North Africa but rescued 80 people Monday from two boats and recovered the bodies of 13 dead migrants in the Alboran Sea, part of the western Mediterranean route into Europe. In a separate incident, the Spanish Civil Guard says it found four bodies of migrants and 22 survivors, all men from northern Africa, after their wooden dinghy hit a reef. (Javier Fergo/AP)

News of the probe into the Navy’s rescue efforts came in the midst of a busy day for rescuers patrolling the Mediterranean Sea.

Spanish rescue workers are searching the seas and shores of southern Spain, looking for around 17 missing migrants trying to reach Europe in smuggling boats departing from North Africa.

The Spanish Civil Guard also said Tuesday said it had found four bodies of migrants and 22 survivors Monday, all men from northern Africa, after their wooden dinghy hit a reef close to the coast west of the Strait of Gibraltar. The Civil Guard said 13 of the survivors were thought to be unaccompanied minors. It also said the 17 missing people traveling with the group could have reached Spanish shores.

The Civil Guard resumed search operations Tuesday both on the sea and along the shore.

Members of Spanish Civil Guard with the help of a helicopter look for bodies of drowned migrants near the village of Canos de Meca in southern Spain on Tuesday. (Javier Fergo/AP)
Members of Spanish Civil Guard with the help of a helicopter look for bodies of drowned migrants near the village of Canos de Meca in southern Spain on Tuesday. (Javier Fergo/AP)

Earlier on Monday, the Spanish sea rescuers found 80 people, including five women, and recovered the bodies of 13 dead migrants in the Alboran Sea, a part of the western Mediterranean migrant route into Europe.

The U.N. says over 2,160 people have died trying to cross the Mediterranean to Europe this year.