A distress signal was picked up from the three-mast SV Concordia about 5 p.m. Thursday, the navy said in a statement. Three hours later, an air force plane spotted life rafts floating in the ocean about 500 km off the coast of Rio de Janeiro.

Forty-eight students — in grades 11, 12 and university freshmen — were aboard the vessel, said Kate Knight, head of West Island College International of Lunenburg, Nova Scotia, which operates the Class Afloat program.

Navy spokeswoman Maria Padilha said the students spent up to 16 hours on life boats before they were rescued by three passing cargo ships between 4 a.m. and 9 a.m. She said the students would be moved to a navy ship and taken to Rio, but did not give an estimate on when they would arrive.

Shelley Piller, whose 17-year-old stepdaughter Alicia was on board, told The Associated Press in a telephone interview from Kenilworth, Ontario, that she was worried despite hearing news that everyone was safe. “That's my kid. For me I need to actually physically see her to understand that she's safe,” Piller said.