ROBESON COUNTY — Mark Anthony Williamswas accidentally released from jail. He was a federal prisoner, but he was being held in the Robeson County jail.

The county's security was no match for Williams' plan. Some say he should not have even been there.

"The reason federal prisoners end up in county jails is because there are no federal jails," said William Berryhill, theU.S. Marshalfor eastern North Carolina.

He says federal prisons like the one at Butner house only convicted criminals.

Federal prisoners who are awaiting trial, as Williams was, are locked away in nearby county jails until their trial date.

But are these county facilities secure enough to house federal prisoners?

"The record speaks for itself. I've been a U.S. Marshal here in the eastern district of North Carolina for 18 years, and I think I've had less than six escapes from county jails," said Berryhill.

Berryhill says what Williams did is rare, conspiring with his cell mate to switch identities.

Williams' cell mate was a state prisoner in jail for a much lesser crime.

"Many sheriffs have set aside a block of cells just for federal prisoners," said Berryhill.

From now on, that will be the case in the cells of the Robeson County jail.

"We will no longer house the state inmates with the federal inmates," said Sheriff Glenn Maynor.

Out of the 44 counties in the eastern North Carolina district, 27 county jails do house federal prisoners awaiting trials.

U.S. Marshals do inspect those facilities before they are approved to hold federal prisoners.