Image copyright AP Image caption Train driver Brandon Bostian pictured in 2007 when he was a conductor

President Obama has said the US must invest more in its infrastructure, in the wake of a train derailment in Philadelphia that claimed eight lives.

He said he was talking to congressional leaders to secure passage of a transport bill.

It's not yet clear what caused Amtrak Train 188 to crash on Tuesday night, leaving more than 200 people injured.

Investigators said on Thursday a camera showed it was speeding up for more than a minute before the crash.

The train was going 70mph (115km/h) about 65 seconds before the video went dark, said Robert Sumwalt of the National Transportation Safety Board.

But 16 seconds before the crash, its speed had increased to 100mph and then hit 106mph as it entered a 50mph zone.

Image copyright AP Image caption Robert Sumwalt tells reporters the latest investigation findings

Image copyright Reuters Image caption Track workers survey the wreckage

Driver Brandon Bostian will be speaking to investigators in the coming days.

He has already said he has no recollection of the accident, and it is still unclear to those investigating why the train was speeding up.

Mr Sumwalt said they have found no faults with the track, signals or the train itself.

It had left Philadelphia's 30th Street Station on time, he added.

How the train speeded up

65 seconds from impact - above 70mph

43 seconds - above 80mph

31 seconds - 90mph

16 seconds - 100 mph

Source: NTSB (camera mounted on train)

A speed control system called Positive Train Control had not yet been installed in that area, unlike other parts of the route along Amtrak's Northeast Corridor.

That has sparked a row in Congress about whether funding was an issue.

President Obama's comments came as he concluded a summit with Arab leaders near Washington.

He said: "We are a growing country with a growing economy and we need to invest in the infrastructure that keeps us that way, not just when something bad happens, like a bridge collapse or a train derailment. That's what great countries do."

Image copyright AP Image caption Mourners at Medgar Evers College, where Derrick Griffith worked

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

Congress has only two weeks before federal funding for transport infrastructure expires, but the cash flow is likely to be temporarily extended.

Meanwhile, an Amtrak employee injured in the derailment has filed what appears to be the first lawsuit.

A lawyer representing Bruce Phillips, who was travelling as a passenger on the train, said he was still being treated in hospital for concussion and spinal injuries, and seeks damages in excess of $150,000.

Image caption Clockwise from top left: Derrick Griffith, Rachel Jacobs, Robert Glidersleeve, Justin Zemser, Jim Gaines and Abid Gilani

The victims

Jim Gaines , a 48-year-old software architect for the Associated Press

, a 48-year-old software architect for the Associated Press Justin Zemser , a 20-year-old Navy Midshipman, who was visiting family in New York

, a 20-year-old Navy Midshipman, who was visiting family in New York Abid Gilani was Wells Fargo senior vice-president

was Wells Fargo senior vice-president Rachel Jacobs , a CEO of a small tech company and mother of a two-year-old son

, a CEO of a small tech company and mother of a two-year-old son Derrick Griffith , a dean of student affairs for New York's Medgar Evers College

, a dean of student affairs for New York's Medgar Evers College Bob Gildersleeve , 45-year-old vice president of EcoLab, a food safety company

, 45-year-old vice president of EcoLab, a food safety company Giuseppe Piras , 41, of Italy, who was in the US on a business trip

, 41, of Italy, who was in the US on a business trip Laura Finamore, 47, of Manhattan, who was returning from a memorial service in Washington

The victims of the Amtrak derailment

Amtrak disaster as political football