PARIS (AP) – A French naval frigate conducting a surveillance mission off Malta discovered the bodies of 18 people floating in the Mediterranean Friday, a navy spokesman said.

Crew members on “La Motte Picquet” noticed no boat nearby as the bodies – possibly of illegal immigrants hoping to reach Europe – were pulled out of the water, said Commander Emmanuel Dinh by telephone from the southwestern port city of Toulon.

Search efforts were completed Friday evening, and the vessel was returning toward France. The bodies were believed to have been floating in the sea for two or three days, Commander Dinh said.

Based on the state of decomposition of the bodies, “it will be difficult to identify the people” – much less track down their family members, he added. Commander Dinh said such a discovery was “not common,” and “is clearly hard on the crew members.”

The European Union has been stepping up patrols off the coast of Africa to keep people from embarking on dangerous trips in overcrowded wooden boats in search of a new life in Europe. Many thousands attempt the crossings each year, and hundreds die along the way.

A major thoroughfare for illegal immigrants seeking entry into Europe is on small, crowded boats between Africa and Spain’s Canary Islands in the Atlantic Ocean. More than 30,000 illegal voyagers were intercepted on that route last year, and another 500 died en route.

A 15-year-old girl drowned off a Greek island in April after human traffickers threw her and other Kurdish migrants overboard, authorities in Greece said then. Nine others were rescued.