Police refused to say if the suspect was the same man who recently moved in with the victims, 42-year-old Chris Hall and fiancee Danielle Greenway, 32. That man was picked up at the house by police Thursday, neighbors said.
Charges likely are the next step, said Allen Park Police Chief James Wilkewitz, who called the deaths "heinous" and not a random act. The suspect's name was not released.
Two bodies with no feet, heads or hands were found Tuesday in the Detroit River and a canal that feeds the river, a mile-wide body of water that separates Detroit from Windsor, Ontario. A circular saw and a suitcase were also discovered. Relatives of the victims reported them missing Wednesday after having no contact for at least five days.
"It makes my heart drop," neighbor Samantha Dolliver said. "They were the sweetest people. It hasn't hit me yet. But when it does, I'm going to barricade myself in a room with a pillow and cry. ... They were human beings, not a piece of scrap metal."
Police released few details at a news conference Friday but asked for the public's help in locating Greenway's van, a tan 2005 GMC Safari with Michigan license plate 7JCM9.
"We still have a lot of work left to do," Detroit Police Chief Ralph Godbee said.
Meanwhile, yellow police tape was stretched around the home while a state police evidence technician, wearing gloves and foot protection, went in and out. A car and a boat were parked in the driveway.
A Greenway family friend, April Purdin, told The Associated Press that the man who was living in the home was Greenway's ex-boyfriend. Dolliver said she knew him only as "Roger" and that he arrived about three weeks ago.
Dolliver said Hall's sister was searching for the couple Wednesday and pounded on the couple's door. She had no luck.
"She said she had a feeling in the pit of her stomach that something was wrong," Dolliver said.
Dolliver's father, Richard, also a neighbor, said Hall was an electrician and Greenway worked for a cleaning service. He last saw them about a week ago.
"She made us cookies and banana-nut bread all the time," he said of Greenway.
Richard Dolliver said he asked Greenway about the man who moved in.
"She said he was a friend who needed help," he recalled.