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ROME, Aug 3 (Reuters) - A Russian researcher was missing after a marine research boat collided with a cargo ship off the Sicilian coast and sank on Friday, the Italian coastguard said.

Thirteen of the 14 people on the 30-metre long research boat were initially feared missing, before all but one were rescued and taken to a local hospital.

The cause of the collision was not immediately clear, but officials said a blazing summer sun had created foggy conditions on the generally calm sea.

"All of a sudden we were covered by a shadow, we turned around and saw the giant bow of this cargo ship bearing down toward us," Giusi Buscaino and Vincenzo di Stefano, two of the rescued researchers, told ANSA news agency.

"In a second, it cut the boat in two like a knife through butter, and we found ourselves in the sea."

The local magistrate's office and the coastguard began probes into the incident while Italy's transport minister headed to Sicily, questioning why radar devices had failed to prevent the collision.

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