PLYMOUTH, Mich. (WXYZ) — Detroit police have opened an investigation after they find the wrong bodies in graves that were supposed to hold six unidentified victims of homicide.

"There's no explanation," said Detroit Police Deputy Chief Marlon Wilson Wednesday. "That's why we had to do a search warrant for the records to try to identify the reason ourselves."

On June 19, Detroit police exhumed seven bodies at United Memorial Gardens in Plymouth. Cemetery workers had flagged the seven plots, but in six of them, police said the bodies were not those of their homicide victims. In fact, they did not appear to have been victims of crimes.

The findings have now launched a probe by the State of Michigan.

A spokesperson for the Department Of Licensing And Regulatory (LARA) released the following statement: "LARA currently has an open investigation regarding the establishment and I cannot comment further at this time."

Police said some of their victims died from gunshot wounds. The youngest was a day old infant and the oldest was a 45-year-old person. And their murders go back as far as 30 years.

We're told investigators from the state and medical examiner's office will now be trying to figure out the names of the six people whose remains were found in the graves.

The exhumations at United Memorial Park in Plymouth and Knollwood Park Cemetery in Canton are part of Operation UNITED (Unknown Names Identified Through Exhumation and DNA).

The project that was launched in May by Detroit Police and their law enforcement partners and it's aimed at identifying homicide victims that date back to 1959 and currently do not have DNA on file.

Police said the seven exhumations they conducted at Knollwood in Canton all resulted in successful identifications through DNA.

Sources said police will return to United Memorial Gardens to find the six remains they were looking for as well as other unidentified victims of homicide that were buried there.