An investigation into the scandal was launched in March 2010 when a supervisor noticed discrepencies in one officer's ticket book, police said.
The probe revealed some officers assigned to the traffic division had falsified information on tickets to collect overtime they did not work.
Police Chief Jeffrey Halstead fired six of the officers in December. They were identified only by their first initials: R. Peoples, P. Aguilar, J. Dunn, M. Middleton, M. Mosqueda and R. Wigginton.
The others had resigned earlier.
The FBI and at least one other federal agency were investigating but decided to let Tarrant County prosecute the case, said Tarrant County assistant district attorney David Lobingier. Some of the overtime was paid with federal grand money in a program known as Selective Traffic Enforcement Program, or STEP.
"The investigation is over," Lobingier said. "We're looking at presenting the case to a grand jury in the next 60 days."
Charges could include tampering with a government record, which is a felony punishable by up to two years in a state jail.
"The fate of all nine now rests in the hands of the judicial system," Halstead said in December. "Maintaining public safety while maintaining the public's trust is a crucial component of our relationship with the community we serve. Integrity matters and I will always safeguard the public's trust by aggressively investigating allegations of misconduct and taking decisive action."