Update: Wednesday, May 13, 12:55 p.m. EDT

The death toll is now at 7, the Philadelphia Police Department tells NBC News. According to NBC News, hospitals treated more than 200 patients. Also, authorities have recovered the black box, Philadelphia Mayor Michael Nutter announced.  

Update: Wednesday, May 13, 12:18 a.m. EDT

Philadelphia Mayor Michael Nutter confirmed at least five fatalities during a press conference late Tuesday night.

"It is an absolute disastrous mess," Nutter told reporters. "Never seen anything like this in my life."

Nutter declined to comment as to why the derailment occurred. The incident is considered level three due to the number of people involved. Six of the injured are in critical condition.

Update Wednesday, May 13, 12:09 a.m. EDT:
 Live stream coverage

An Amtrak train derailed on Tuesday night. The train was headed from Washington D.C. to New York when it derailed around 9:45 p.m. EDT, according to The New York Times. There were five crew members and about 240 passengers on board, including former Representative Patrick Murphy who posted a photo on his Twitter account shortly after the crash.

Eight to ten train cars left the tracks and so far, the number of passengers injured is at 50, but that number may climb as the fire department and search and rescue go car-to-car, according to NBC 10 Philadelphia.

Amtrak posted on Twitter that all services between New York and Philadelphia are cancelled. Amtrak also encouraged concerned family members of train 188 passengers to call Amtrak's Emergency Hotline at 800-523-9101.

This is a developing story.