The agreement has been in place for more than a decade and allows the state to house those inmates until federal beds open up. Typically, he said, they don't stay long.
Although State Police are investigating and would bring any charges, DeLong said the authority is also conducting an internal review.
"Unfortunately,'' he said, "sometimes inmate-on-inmate assaults are unavoidable.''
DeLong said the jails are full of potentially violent offenders, regardless of whether their crimes violated state or federal laws. The jurisdiction is seldom an indicator of what kind of inmate they'll be.
Those who have already been through the system and sentenced are typically easier to classify than "the turnkey jail population,'' whose formal charges may not indicate whether they also have problems with violence, drugs or mental illness.
"As far as the arresting jurisdiction goes,'' DeLong said, "it doesn't really matter.''
In a review last summer, The Associated Press found that the number of inmate-on-inmate attacks in state prisons surged from 64 in 2007 to 148 last year, even though half the population was in for a nonviolent offense.
In the 10 regional jails, inmate-on-inmate assaults jumped nearly 25 percent between 2007 and 2011.
The Justice Center at the nonpartisan Council of State Governments is currently reviewing West Virginia's correctional system with an eye to addressing at-capacity prisons and overcrowded jails without sacrificing public safety.
While West Virginia ranks 32nd among states for its rate of putting adults behind bars, it is leading them all in prison population growth.