The victims were identified as Abraham Ramos, 29, of Palatine, and Hannah Tammeling, 22, of Plainfield, according to the Will County Coroner's Office.
The pair died of drowning, according to preliminary findings. Final cause of death is pending a police investigation and toxicology reporters, the coroner's office said.
The 29-year-old man's body was found Monday morning and the 22-year-old woman's body was found a few hours later.
Troy Fire Protection Fire Chief Andy Doyle said the activity from search boats up and down the river likely "dislodged her from the bottom of the river."
The actual discovery of the woman's body appears to have been made by a couple walking along the shoreline.
Just before 6 p.m. Sunday, a witness saw the two individuals go into the water at Hammel Woods Forest Preserve and alerted a Will County sheriff's deputy. That deputy saw both the man and the woman being pulled into the dam.
He lost sight of them and then one of the firefighters from the Troy Fire Protection District saw the man and was unable to reach him.
Authorities believe the man went in first. They don't know why or how he got into the water. They believe the woman went in after to save him, near a very dangerous dam.
"The dam over here in Hammel Woods is very dangerous," Doyle said. "It may not look dangerous to a lot of people, but once you get into the dam there is a boil that keeps turning and turning and sucks you back in against the dam and that is where a lot of the danger is, along the dam and within a couple feet of the dam."
The forest preserve in the area is closed. Crews searched a span of 2.5 miles of the DuPage River.
Some people who live in the area spoke about the dangers of the river.
"There's a lot of signs...down river warning people about the current and the undertow," said resident Brad Kanapkiewicz.
"The locals know not to, especially when the river is up," said resident James Webster. "It ain't up that much, a foot, foot-and-a-half, but it's up enough."