LISBON, Portugal — Investigators sifted through the wreckage of a streetcar in downtown Lisbon on Thursday, trying to determine why the popular tourist attraction derailed during the busy summer season, killing 16 people and injuring 21, five of them seriously.

The Elevador da Gloria came off its rails during the evening rush hour Wednesday when it was packed with locals and international tourists. Officials cordoned off the crash site, and were taking photographs and pulling up a metal cable from beneath the rails that climb one of the Portuguese capital's steep hills.

"This tragedy … goes beyond our borders," Prime Minister Luis Montenegro said at his official residence, calling it "one of the biggest tragedies of our recent past." Portugal observed a national day of mourning Thursday.

See Full Page