By Richard Cowan
WASHINGTON, June 2 (Reuters) - Human error remains a strong focus of the inquiry into the Philadelphia Amtrak crash, but federal investigators are still digging for answers, aides said ahead of the first hearing in the U.S. Congress on last month's deadly accident.
House Republican aides told reporters on Monday that investigators might suspect human error caused Amtrak Train 188 to hit speeds of 106 miles per hour (171 km per hour) in a zone with a 50-mph (80-kph) speed limit.
Transportation safety officials are set to appear on Tuesday before a congressional panel to discuss their investigation into the May 12 derailment that killed eight people and injured about 200 when the speeding train left the tracks on a sharp curve.
Christopher Hart, chairman of the National Transportation Safety Board, is scheduled to testify to the House of Representatives' Transportation and Infrastructure Committee.
The House aides noted they did not yet know if investigators had settled on any theory for the cause of the crash. But if it was mechanical problems, the aides said, regulators likely would have acted by now by ordering checks of similar locomotives.
Aides said investigators were analyzing the cell phone records of 32-year-old engineer Brandon Bostian. "They are trying to figure out when exactly either texts or emails or phone calls were made and then try to line them up to where the locomotive and the train actually were," said one aide.
Bostian's attorney Robert Goggin has said Bostian had turned off his cell phone, as Amtrak requires of all engineers behind the controls.
Joining Hart at the witness table will be Amtrak President Joseph Boardman; Sarah Feinberg, acting administrator of the Federal Railroad Administration; and Dennis Pierce, who heads the Brotherhood of Locomotive Engineers and Trainmen.
Tuesday's hearing is likely to see some political jockeying by lawmakers amid the expert testimony.
The day after the crash, House Republicans approved $1.14 billion in funding for Amtrak next year, $262 million less than the current level and well below the $2.45 billion requested by Democratic President Barack Obama.
House Speaker John Boehner, a Republican, has rejected any suggestion that the level of Amtrak's federal subsidies, at a time of fiscal restraint, contributed to the Philadelphia train derailment. (Additional reporting by Susan Cornwell; Editing by Kevin Drawbaugh and Lisa Shumaker)