A senior FBI agent says there's concern over a growing number of teenagers staging armed bank robberies around the United States.

Jennifer Leonard, a supervisor in the agency's violent crimes unit in Washington, told the Cincinnati Enquirer all field offices have been advised to monitor ages of suspects, but said this year's activity wasn't strong enough to call a pattern.

"We're looking to see if it's isolated or if it's an emerging trend," Leonard said.

Most recently, a 17-year-old Bloomington, Ind., girl was charged in a July 8 bank robbery. In March, a 17-year-old boy in Nashville was also arrested after a bank robbery, and later this month, a 15-year-old Lima, Ohio, girl will be sentenced for her role in a credit union heist that was cracked when she left her book bag in a getaway car.

The teen told police after being arrested the adult who entered the bank with her and their adult driver headed to Chicago with their $5,000 haul and spent it on drugs and shopping, the newspaper said.