PHOENIX — Nearly 5,000 Arizona immigrant detainees with criminal records were released from custody, a federal agency has acknowledged.

Of those, 121 later committed fatal crimes.

The National Review reported that the Department of Homeland Security said that the detainees charged with murder had been jailed and let out from 2010 to 2014.

A letter from the director of Immigrations and Customs, Sarah Saldana, to U.S. Sen. Jeff Flake (R-Ariz.) and Senate Judiciary Chairman Chuck Grassley was recently made public.

The senators asked asked for details surrounding the release of Valley resident Apolinar Altamirano, who was charged with the shooting death of a Mesa convenience store clerk in January. Altamirano was awaiting a deportation hearing.

Immigrations and Customs Enforcement had taken Altamirano into custody in January 2013 after he was convicted on burglary charges.

He was later determined eligible for bail.

According to an ICE report, in 2014 the agency said “63,159 of the convicted criminal removals were Level 1 offenders.”

Priority 1 offenders are determined to be threats to national security, border security and public safety.

The department has been under fire since a 2013 revelation that it had let over 2,000 immigrants out of jail.