Prosecutors in Sicily are examining allegations by shipwreck survivors that a US navy ship ignored distress calls and failed to assist them before their dinghy capsized.

The USS Trenton rescued 42 people after the dinghy sank on 12 June, but survivors allege that the cruiser had earlier ignored their cries for help, failing to avert a disaster in which 76 people died.

Magistrates in Ragusa confirmed that they have examined a video published by La Repubblica in which six survivors say the US cruiser was near the boat before the sinking – but appeared to ignore their request for help.

“We saw that ship, it was not far away,’’ said one of the survivors in the video. “We saw the American flag. If they had rescued us when we were all still onboard, 76 people would not have died.”

The dingy had left Libya a few days earlier with 117 migrants onboard, most of them from sub-Saharan Africa. Survivors said that in the early hours of 12June, the vessel started to take on water, not long before they first sighted the Trenton.

‘‘The sea was rough and our boat began to fill with water,” one survivorsaid, “and we suddenly saw a ship; it was an American ship.”

The survivors say they tried to attract the attention of the ship’s crew for an hour. “We saw the American flag and we tried to reach them, but as we approached, they seemed to avoid us and changed direction,” said another.

The US navy has denied that the Trenton was at the scene before the sinking.

The migrants’ boat eventually sank, killing 76 people. ‘‘I saw my only brother and sister die and thought I would soon die too,’’ a Nigerian woman told La Repubblica.

Another survivor said: “My wife was pregnant. She died before my eyes.”

The survivors said that the Trenton returned to the scene half an hour after the sinking. “We clearly saw the same American ship that had ignored us approaching,’’ one man said in the video.

Interviewed by La Repubblica, the rescued migrants said that when they had asked why the Trenton had not intervened before the sinking, they were told that “it was not their job”.

Authorities in Ragusa are now examining the video interviews, although prosecutor Fabio D’Anna said a formal investigation has not yet been launched. “We will try to talk with the survivors of the shipwreck, to understand what happened that morning,” D’Anna said.

Cmdr Kyle Raines, a spokesman for the US 6th Fleet, said: “We are aware of the reports that an Italian official is looking into USNS Trenton’s rescue of people in distress at sea.

“Military Sealift Command reaffirms that at approximately 1010 GMC on 12 June 2018, USNS Trenton’s watch officer visual observed a capsized raft and personnel floating in the ocean. This was the first observation of the raft made by personnel of USNS Trenton.

“Two rigid-hull inflatable boats (RHIBs) and one fast rescue boat were launched from Trenton and recovered the distressed people, who were immediately brought aboard Trenton and provided with food, water, clothing and medical care.”

But further questions over the Trenton’s response to migrants in danger were raised by another recording made by a reporter from La Repubblica who was on the German charity ship Sea Watch in June.

Fabio Butera recorded a radio conversation between the Trenton and a Greek merchant vessel, Leone Hermes, which suggests that the Americans might have ignored another rescue request two days before from migrants drifting in an overloaded raft.

The recording makes it clear that the crew of the Leone Hermes reported the presence of a distressed raft to the US ship on 10 June. An American voice can be heard replying: “I have other tasking which I’m following … We are unable to assist in this matter.”

In that case the migrants were recovered by the Leone Hermes.