A maintenance worker has been arrested and charged with helping 10 inmates carry out a brazen escape from a New Orleans jail last week, bolstering the suspicion among investigators that the escape would have been impossible without inside help.

The worker, Sterling Williams, 33, who was arrested on Monday, shut off water at the jail, allowing the inmates to remove a metal toilet and sink fixture from a cell wall, the Louisiana attorney general’s office said. Mr. Williams told investigators that an inmate had threatened to “shank him” if he did not shut off the water, according to an affidavit supporting his arrest.

The inmates then used an unidentified tool to cut steel bars behind the cell room sink, leaving behind a hole in the wall just big enough to crawl through and a taunting misspelled message: “to easy LOL.”

The inmates left the jail through a loading dock, scaled a wall, using blankets to protect themselves from barbed wire, and ran across Interstate 10. A civilian employee of the sheriff’s office, who was the only person monitoring security systems in the part of the jail where the escape occurred, had left his station at the time to get food, officials said last week.

According to the affidavit, Mr. Williams told agents from the Louisiana Bureau of Investigation that an inmate with tattoos on his face, whom he called “Massey,” but whose full name is Antoine Massey, “threatened to shank him if he did not turn the water off.”

Instead of reporting the threat, Mr. Williams told agents that he went into a pipe chase — an area where plumbing is concealed behind a wall — and turned off the water by closing a valve, the affidavit states.

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