Women's rights groups in Egypt said they are working with authorities to gather more information about the attempted honor killing, Bikyamasr.com reported Wednesday.
"If this is really what happened, then it shows there is a lot of work to counter honor violence in this country, where women and girls are killed because, simply, they are women," said Nora Tarek, a women's rights researcher in Cairo.
The young woman initially refused to marry the elderly man but later bowed to family pressure, Bikyamasr.com reported.
Her parents tossed her into the river when she returned home after divorcing him.
Last year, a 22-year-old Egyptian woman was found dead on a coastal road with a noose around her neck. A family member said the woman was killed by her brother for leaving home with a stranger.