Image copyright NTSB Image caption Investigators are analysing the data recorder to learn what caused the crash

An Amtrak train that derailed in Philadelphia, killing at least seven people, was travelling at twice the speed limit, say safety experts.

The driver applied the emergency brakes when the train hit 106mph (170km/h) on a 50mph track, said the National Transportation Safety Board (NTSB).

But his efforts had only brought the speed down to 102mph when the deadly crash happened.

He has been identified in US media as 32-year-old Brandon Bostian.

''He remembers going to that area generally, [but] has absolutely no recollection of the incident or anything unusual," his attorney Robert Goggin told ABC.

Image copyright Getty Images Image caption The New York National Guard has deployed to Philadelphia to assist local authorities

Robert Sumwalt of the NTSB told reporters a speed control system had not yet been installed in that area, unlike other parts of the route along Amtrak's Northeast Corridor.

"We feel that had such a system been installed in this section of track, this accident would not have occurred," he said.

Amtrak Train 188 was going from Washington to New York when it derailed on Tuesday night, leaving more 200 people injured.

The death toll rose from six to seven on Wednesday, as another body was found by the search and rescue team.

Image copyright AP Image caption Hundreds of people were taken to hospital, and seven have died

Five victims have been publicly identified so far:

Jim Gaines, a 48-year-old father of two and software architect for the Associated Press, was travelling home to New Jersey following a work conference in Washington DC

Justin Zemser, a-20 year-old Navy Midshipman, was on leave from the Naval Academy in Maryland, and was visiting family in New York

Wells Fargo senior vice-president Abid Gilani, the company confirmed

Rachel Jacobs, a CEO of a small tech company and mother of a 2-year-old son.

Dr Derrick Griffith, a dean of student affairs for New York's Medgar Evers College.

One man has been confirmed missing.

Robert Gildersleeve, an executive with a chemical company, had dropped off his son at lacrosse practice before boarding the train.

One of the busiest stretches of passenger rail in the country, between Philadelphia and New York, is closed as officials continue to try to establish exactly what happened.

President Obama said he was "shocked and deeply saddened to hear of the derailment".

Image copyright AP

As emergency crews continued to dig through the wreckage, lawmakers in Washington debated the future of Amtrak's budget, with one spending committee voting to slash their funding by almost a fifth.

"We are divesting from America," accused one member of Congress.

"Don't use this tragedy in that way," another Congressman responded angrily.

Congress has only 18 more days before federal funding for transportation infrastructure expires, but the funding is likely to be temporarily extended.

Amtrak is a national publicly funded rail service, serving tens of millions of people every year.

The crash happened not far from the site of a derailment in 1943 that killed 79 people, one of the worst train accidents in the US.

A train travelling at almost twice the speed limit crashed in Spain in 2013, also killing 79 people.