Eleven inmates have escaped from a New Orleans jail, and law enforcement officials searching for them on Friday warned that they should be considered “armed and dangerous.”

The Orleans Parish Sheriff’s Office did not disclose how the inmates had managed to escape from the jail, called the Orleans Parish Justice Center, but it warned that anyone who harbored them or helped them evade law enforcement could be prosecuted.

The Louisiana State Police said later on Friday that troopers had arrested one of the escapees, Kendell Myles, in the French Quarter of New Orleans.

“Troopers continue to work closely with our local, state and federal partners as the search remains active for the remaining escapees,” the state police said.

Officials noticed during a routine head count at 8:30 a.m. on Friday that the detainees were missing, Sheriff Susan Hutson said, though she did not specify when they had escaped. The office then activated “emergency protocols” and began a search for the inmates, she said.

“We are actively working with local, state and federal law enforcement agencies in a full-scale search operation,” Sheriff Hutson said. She said the office urged members of the public to remain alert and to notify law enforcement if they had information that could aid in the search.