Last updated: May 18, 2015, 12:58 p.m.
Here are the latest things to know about the derailment of Amtrak Train 188.
1. Projectile probed: It remains unclear whether the derailed train was struck by a projectile in the moments before the crash. A conductor told investigators on Friday that she overheard a radio conversation in which Train 188 engineer Brandon Bostian said his train had been hit. But the 32-year-old engineer apparently didn't radio his dispatchers with that report, a National Transportation Safety Board official said Sunday. Two other trains -- a SEPTA Regional Rail train and an Amtrak Acela -- have reported being hit by something around the same time that night. The NTSB says the projectile is one of many angles being investigated, and the FBI will examine the train's windshield.