Leon Rodriguez, director of US Citizenship and Immigration Services, attends a naturalization ceremony at George Washington’s Mount Vernon in Mount Vernon, Va. last month. EPA/MICHAEL REYNOLDS

A green card is like a green light for foreigners living in the United States.

Officially called permanent resident cards, they authorize holders to live and work here. Given the millions of people who reside here illegally, the documents are a valuable commodity among those who can’t get them through proper channels.

So when the government sends cards to the wrong address, it’s a big problem for those who should have them but don’t and for government officials who wince at the thought of the cards in the wrong hands.

Now comes word that since the U.S. Customs and Immigration Services (CIS) installed its Electronic Immigration System (ELIS) in 2012, the number of cards going to the wrong places has only increased.

By how much, no one seems to know.

In this age of terror, this can be more serious than an employee working without proper papers.

A new report from the office of John Roth, the inspector general in the Department of Homeland Security, which includes customs and immigration, says officials acknowledge there is “no accurate means of identifying the exact number of potentially hundreds of cards sent to incorrect addresses for cases processed in ELIS.”

As seems to be the case repeatedly in government lately, the blame goes to the computer systems, as if they are beyond the control of chief information officers. But that’s apparently the case at CIS.

The report says the cards were sent erroneously “due to a system limitation” that prevented humans from changing the addresses. Even when green card holders requested a change of address, employees could not update the system.

“Further,” the report continued, “the system did not always accurately display address information, often eliminating or cutting off critical elements such as apartment numbers.”

The report said Customs and Immigration officials told investigators the “only option for addressing the problem of incorrect addresses was to manually send out notices with instructions on how to mail the cards back.”