(CNN) - Officers for the Transportation Security Administration could soon be replaced by machines.
The agency started testing the boarding pass check-in machines in Washington, D.C. last week, and the program expands to Houston Tuesday.
The machines are geared to recognize all valid identification, ranging from driver's licenses to tribal IDs and U.S. and foreign passports.
TSA hopes the machines will do a more efficient job weeding out fraudulent documents and getting passengers to their planes.
The review of the machines is expected to last several months.
The first 30 machines cost more than $3 million.