Unknown number of U.S. permanent residents stuck overseas as a result of Trump's immigration ban 

Trump signs orders to limit refugees, review military readiness

This is our look at President Trump\'s administration and the rest of Washington:

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An undetermined number of longtime U.S. residents have been stranded overseas as a result of President Trump\'s executive order temporarily blocking visas from seven countries in the Middle East and North Africa.

All visa holders from those seven countries are now barred entry to the U.S., including lawful permanent residents, also known as green card holders, people with U.S. work visas and other types of visas, according to a senior U.S. immigration official. The official spoke on condition of anonymity to discuss internal deliberations.

Some of the affected countries, such as Yemen and Libya, have relatively few nationals who are U.S. permanent residents or visa holders. But a large number of Iranians have permanent residency in the U.S., as do smaller numbers from some of the other countries on the list, which includes Iraq, Syria, Somalia and Sudan.

Trump\'s executive order, issued Friday, immediately affected longtime foreign residents of the U.S. who were overseas at the time the order was signed, as well as any high-skilled tech workers or other work-visa holders from those seven countries caught outside the U.S. as of Friday.

Lawyers at the Department of Homeland Security are examining Trump\'s executive order and drafting instructions for border officials, the official said.

Eventually, the administration may set up a way for some visa holders to apply for a waiver from the ban, but that is still being deliberated and will take time to set up, the official said.

Lawyers at DHS are scrambling to understand the order and parse out what it means for procedures at airport checkpoints and ports of entry around the country.

Most senior DHS officials were not aware of the coming changes before they were released Friday. Immigration and customs officers are struggling to figure out which incoming travelers to let in while at the same time keep up with the normal flow of travel, the senior US immigration official said.

11:17 a.m.: This article was updated with more background.