The Bureau of Prisons (BOP) wrote in an emailed statement that two prisoners died in hospital near the prison in Beaumont, Texas, where the violence erupted. Two other prisoners were taken to hospital but no details on their condition were released.

The BOP said it acted in an “abundance of caution” in ordering the nationwide lockdown, a rare event that sees inmates confined to their cells, calling it a “temporary measure to ensure the good order of our institutions.”

There are more than 134,000 prisoners housed in 130 federal prisons in the United States.

“We anticipate this security measure will be short-lived,” the BOP said in the statement. “The BOP will continue to monitor events carefully and will adjust its operations accordingly as the situation evolves.”

No more details were provided.

The New York Times, citing unidentified sources, reported that the members of the violent Salvadoran street gang MS-13 were involved in the fighting at the prison in Beaumont, stoking fears that the violence could spread to other prisons as rival gang members sought retribution.

This month, BOP director Michael Carvajal said he would retire, though remain in his position until a new director is found. Carvajal had come under criticism for his leadership, especially in dealing with the coronavirus pandemic.

(Reporting by Brad Brooks in Lubbock, Texas. Editing by Robert Birsel)