President Bronislaw Komorowski and Prime Minister Donald Tusk have both visited the site where two trains, carrying about 350 people in total, crashed near the town of Szczekociny while traveling toward each other on the same track on the evening of March 3.
The cause of the crash is yet to be determined.
Rescue workers toiled overnight to pull survivors from the wreckage of the crash.
An emergency services spokesman confirmed 16 deaths, but said more fatalities could not be ruled out.
The crash is the worst rail accident in Poland in more than two decades