EL PASO, Texas — The federal agency tasked with overseeing security at transportation hubs has been violating its own policy by allowing migrants who have been released from federal custody onto flights despite not having required documents, according to several Department of Homeland Security officials.

For the past six months, the Transportation Security Administration has allowed migrants released from the custody of other Homeland Security agencies to board flights to other parts of the country despite the passengers lacking any of the 15 documents it states are the only acceptable forms of identification.

Since early December, the agency has avoided temporarily changing federal policy and also not introduced a permanent solution to address this new phenomenon, despite no indication border apprehensions and mass releases are slowing down any time soon.

Since January, Immigration and Customs Enforcement has released from custody more than 200,000 migrants who arrived at the border as part of a family. The releases are mandatory under a 2015 court ruling that bars ICE from holding families more than 20 days.

ICE often drops people off at bus stations, where nongovernmental organizations that have been alerted to the drop-offs send volunteers to help migrants make travel arrangements to join family members in other cities. The agency then wipes its hands clean following the releases. ICE would not comment on the legal precedent for undocumented immigrants boarding flights in the U.S.

So instead, those looking to depart the border via regional airports become TSA's burden. If TSA chose to turn away people at airports it would apply more pressure to overwhelmed bus companies like Greyhound and local motels in border towns, complicating an already dire situation for localities struggling to care for this demographic.

TSA was unaware initially which documents its security officers required for migrants to board flights.

Its website states passengers over the age of 18 who are boarding domestic or international flights out of the U.S. "must show valid identification at the airport checkpoint in order to travel."

Those 15 acceptable forms of ID include the USCIS worker's document, as well as a driver's licenses or state ID; U.S. passport or passport card; a DHS-trusted traveler cards; a Defense ID card; permanent resident card; a border crossing card; a DHS-designated enhanced driver's license; a federally recognized, tribal-issued photo ID; an HSPD-12 PIV card; a foreign government-issued passport; a Canadian provincial driver's license or Indian and Northern Affairs Canada card; a transportation worker identification credential; a U.S. Merchant Mariner Credential; and a USCIS Employment Authorization Card (I-766).