"This was the same group that caused a disruption a few days ago and lost their gym privileges," Mades said. "Sunday night was to be their first night back in the gym."
Mades said a female deputy was in charge of the move from B pod at the jail to the gym. Although she was recently hired, the deputy recognized the situation was getting out of hand and locked the 15 inmates into an area between two gates, Mades said.
"Once they couldn't go anywhere, she called for backup," Mades said.
Deputies with pepper spray and other defensive weapons, including the dog, arrived on the scene.
None of those weapons was used, said Mades, who said the dog helped defuse the situation.
Hagerstown City Police Sgt. William Wright said Sunday he was asked for help and sent the one dog he had available.
"One is all they needed," he said. "Apparently, it worked fine."
Lt. Van Evans, warden of the jail, said the police dogs are especially useful when there are a large numbers of unruly prisoners.
Once the inmates were back in their cells, deputies shut off the water for a while to prevent any damage in retaliation for the incident, Mades said.
The seven leaders will be dealt with administratively, Mades said. That could involve moving them to other areas of the jail.
No one was injured.
The jail population Monday was 319 inmates, a jail official said.