A suspect who was taken into custody for the fatal stabbing of a Detroit synagogue leader was released without charges after prosecutors say cops failed to file any paperwork — a possible indication they’re still building their case.

The unidentified suspect was arrested last week in Kalamazoo, Michigan, for the murder of Samantha Woll, but was released on Friday after 72 hours in custody — the most law enforcement can detain someone without a hearing under Michigan law.

“There is nothing before us,” the Wayne County Prosecutor’s Office told Fox News of the absence of a warrant request.

“This must happen before we can review the case for a charging decision,” it explained. “Until then, it is entirely a police investigation that they are continuing to work on.”

But police said the man remains a suspect, and said that when he was brought back to Detroit from Kalamazoo he stopped cooperating and hired an attorney, according to Click On Detroit.

“The homicide investigation into Samantha Woll’s tragic murder is ongoing,” the Detroit Police Department said in a statement.

“Despite recent developments, DPD’s Homicide Unit remains committed to presenting a comprehensive set of facts for submission to the Wayne County Prosecutor’s Office,” it said, adding: “This crime reflects a common challenge in our line of work when an arrest is made as the investigation unfolds.

“We appeal to the community for any information as investigators thoroughly examine every aspect of this case.”

Local defense attorney Edward Bajoka, who isn’t involved in the case, told Fox News Digital that the suspect’s release potentially could mean they’re still building their case.

“This tells me either police don’t have enough evidence to proceed with formal criminal charges, or police interviewed him and cleared him,” said Bajoka, an attorney with the Detroit-based Bajoka Law Group.

He said it’s possible that they arrested him hoping that he would incriminate himself.

The suspect was reportedly arrested after he made an “ambiguous” statement to cops about Woll’s death.

He was said to have known Woll, 40, and even attended her funeral, according to the Detroit Free Press.

The suspect was reportedly arrested after he made an “ambiguous” statement to cops about Woll’s death.

Cops were then seen executing a search warrant at his home last week, the Free Press reported.

Woll, the president of the Isaac Agree Downtown Detroit Synagogue, was found dead outside her home in the city’s Lafayette Park neighborhood, east of downtown, on Oct. 21.

Police said they responded to a 911 call about an unresponsive person around 6:30 a.m. Woll had been at a wedding the previous night and left at about 12:30 a.m., according to police and friends.

Authorities believe she was stabbed inside before stumbling outside fatally wounded.

Throughout the investigation, White has insisted that there was no evidence to suggest the slaying was the result of a hate crime.

“We believe that this particular incident was not motivated by anti-semitism and that this suspect acted alone,” Detroit Police Chief James White told reporters at a press conference on Oct. 23 — when he said investigators were “just short” of naming the suspect.

He said at the time there were “several factors” that led to that conclusion, but declined to comment further.