TULSA, Oklahoma - There are new developments in a 19-year-old Tulsa cold case.

The Tulsa County Cold Case Task Force says it's investigating new leads in the Dena Dean case.

Investigators say they're working on new angles on this case, but can't say what they are yet.

The Dean family feels they're close to a breakthrough.

It's by far the largest case file in the Tulsa County Cold Case Task Force office.

Binders and bins dedicated to one question: What happened to Dena Dean?

Dena Dean, 16, was last seen in June 1998 leaving her job at a west Tulsa grocery store.

Her body was found six days later in a field and her family's been left without answers all this time.

"I don't know what killed her. I don't know if she was shot, stabbed, strangled, whatever," said Larry Dean, her father.

The task force announced it's working on several leads generated by tips that came in shortly after a memorial service for Dena last month.

Her parents feel momentum is building.

Dena Dean's case will even be featured in a series on Investigation Discovery.

"My level of excitement has went from a three or four, up to an eight or nine, maybe even a 10 at times," Larry Dean said.

Investigators even went back to the scene where Dena's body was found on Tuesday, armed with new information and new technology, like a drone to record aerials of the scene.

Investigator Doc Shannon says anything helps.

When you get involved as late as we're involved in it, there's so many things that, in retrospect, we would wish someone had done," Shannon said.

"I think it's a breakthrough. I really think this task force is really going to get us the answers we need," Larry Dean said.

If you have any information on the Dena Dean case, contact the Cold Case Task Force at 918-596-5723.