The FBI is offering an additional $25,000 reward in connection to the Erica Parsons case.
The Rowan County Sheriff's Office was already offering $10,000 in the case.
Thursday marks six months since the teen was reported missing by a family member.
Rowan County Sheriff Kevin Auten and FBI Assistant Special Agent in Charge Deron Roberts announced updates on the case. They are narrowing their scope to one month -- November 2011.
"We've followed hundreds of leads and you have seen many of those investigators steps along the way," Auten said.
In August 2013 Erica Parsons was reported missing -- two years after family members said they saw her last. Authorities remain challenged by the length of time that passed before she was reported missing.
Police have said that they are investigating the case as a homicide.
"We know that there's someone out there that can help us though and now's the time to come forward,” Auten said.
Investigators still question Casey Parsons and Sandy Parsons’ story.
"It is clear that Casey and Sandy Parsons have not been truthful in providing the information that would lead to the whereabouts to find Erica,” Auten said.
The family is in talks with ABC’s 20/20 to create a special report on Erica Parsons.
For complete coverage on the Erica Parsons case, click here.