A seven-year-old Polish boy and his mother have died after falling from a ferry traveling from Sweden to Poland, authorities said on Friday. 

Swedish prosecutors announced the case is being investigated as a homicide to discover what happened, although no suspects have been identified. 

"The investigation aims to try to clarify what happened," prosecutor Stina Brindmark said.

Authorities said Thursday the child fell from the Stena Spirit ferry and his mother plunged into the sea after him in an apparent rescue attempt. The boy fell from a height of about 65ft., according to the Swedish Maritime Administration. 

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A photo of the Stena Line ship

P7XMF7 MS Stena Spirit, large cruiseferry owned by Stena Line, in  Gdynia, Poland. June 24th 2018 (Wojciech Strozyk / Alamy Stock Photo)

Passengers aboard the ferry watched in horror as a helicopter was deployed to find and rescue the missing pair. The two were winched to the helicopter and transported to a Swedish hospital but later died.

The mother was in the water for 59 minutes before the helicopter picked her up, and her son 66 minutes, Polish website Fakt reported. 

Polish police confirmed the deaths after the mother and her son failed to be resuscitated. 

"Unfortunately, in the morning we received information from the Swedish side that we have to pass on this terrible news to the family, because both the boy and the woman are dead," said Polish police spokesman Mariusz Ciarka.

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A photo of the Stena Line ship

2K43A02 MS Stena Spirit, large cruiseferry owned by Stena Line, in Gdynia, Poland (Wojciech Strozyk / Alamy Stock Photo)

The Swedish ferry, the Stena Spirit, had 310 passengers on board and was in the Baltic Sea midway through its journey to Gdynia in Poland from Karlskrona in Sweden when the incident happened, rescue officials said on Thursday.

"At the moment we have no information whether this was due to a malfunction of the ferry," Stena Line spokesperson Agnieszka Zembrzycka told TVN 24, per Reuters. "We are cooperating with the police and other authorities that are appointed to explain the causes and circumstances of this event."

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A Stena Line ferry docked in Gdynia, Poland

Stena Ebba ferry belonging to the Stena Line company serving on the route between Gdynia in Poland and Karlskrona in Sweden is seen in Gdynia, Poland on 17 June 2023 (Michal Fludra/NurPhoto via Getty Images)

Stefan Elfstrom, a spokesman for Stena Line, told the Independent the crew quickly responded once the man overboard alarm was raised. 

"Items have been found that belong to these people, but not the people themselves," Elfstrom said. "Then the alarm went off, the crew looked at the surveillance cameras and saw that two people had fallen into the water.

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"There is little information on whether there were relatives or people who knew the two people on the ferry. However, someone noticed that two people were missing."

Swedish police have asked Polish passengers via Poland's state-run news agency PAP for information that could explain how the accident happened.

Reuters contributed to this report.