Police said former detective Justin LoBurgio worked in Lakewood's Crimes Against Children Unit from 2006 to 2010 before being moved back to patrol. Lakewood police spokesman Steve Davis said allegations then surfaced of LoBurgio improperly investigating the cases.

The department said 30 to 50 cases might even need to be reopened.

"And in a case like this, it's embarrassing," said Davis. "I can tell you that even the chief was extremely upset about this incident."

The detective allegedly failed to properly investigate and thoroughly follow-up with dozens of cases involving potential crimes against children.

"There are no major cases, there are no high profile cases," said Davis. "No homicides."

LoBurgio's apparent poor performance was uncovered when LoBurgio returned to street patrol and his successor noticed closed cases that were unfinished.

"There was certain evidence that wasn't booked into evidence," said Jefferson County district attorney Scott Storey.

7NEWS tried to visit LoBurgio at his home, but a woman there told us he was unavailable.

"I think what we had was someone who was very negligent, overwhelmed and just dropped the ball," said Storey. "And he just kind of gave up, and tried to cover that up. It was not criminal. It was negligent, certainly."

"He's gone. He has resigned from the department," said Davis. "I'm guessing that he could see the writing on the wall. He knew there was severe discipline or termination headed his way."

The DA's office is reviewing 13 open cases that LoBurgio worked on. The D.A. has sent letters to the defense attorneys in each case notifying them of the agent's integrity issues.

Neither the police nor the D.A. believe this negligence put any children's lives at risk.

LoBurgio resigned from the force in January. He was not asked to resign and did so on his own accord, Davis said.

Davis said Lakewood police are reviewing over 200 of the cases LoBurgio was involved in. Police will likely reopen only a fraction of those cases, Davis said.

"We are probably not going to reopen nearly that many," he said. "Maybe 40 or 50 of them."

Watch 7NEWS at 5 p.m. for more on this developing story.