*7 dead in worst accident ever on D.C. subway system
*Subway authorities were warned about safety of older cars
*Part of one train hurled on top of another
By Andy Sullivan
WASHINGTON, June 23 (Reuters) - Transit authorities in Washington, D.C. were warned to upgrade the safety standards of older subway cars before a crash on Monday that killed seven people, U.S. investigators said on Tuesday.
Federal officials investigating the cause of the crash, the deadliest in the 33-year history of Washington's Metro Area Transit Authority, said a 2006 warning to upgrade or retire older, less protected cars had gone unheeded.
"We recommended to WMATA to either retrofit those cars or phase them out of the fleet. They have not been able to do that and our recommendation was not addressed," National Transportation Safety Board spokeswoman Debbie Hersman said at a news conference at the scene of the accident.
Seventy-six people were taken to hospitals after one train slammed into another that was stopped on above-ground tracks during the afternoon rush hour, Washington Mayor Adrian Fenty said. He said there were seven confirmed fatalities.
Two people had been in critical condition but one patient was upgraded overnight, Fenty said.
The operator of the moving train was among those killed in the crash, the impact of which drove one train into the air and on top of the other. It remained there on Tuesday morning as workers attempted to clear the wreckage.
NTSB had urged the Metro system to replace its older subway cars or upgrade their crashworthiness following a 2004 accident that injured 20 passengers, federal records show.
John Catoe, the general manager of the Metro system, said changes to the rail cars would be made if needed.
"Any car that strikes another vehicle at a certain rate of speed and with a certain amount of weight, you're going to have some major damage," he said.
The crash occurred on the heavily traveled Red Line about 5 p.m. EDT (2100 GMT), on the northeastern outskirts of the city near the border with Maryland, on a relatively lengthy stretch of track where trains can build up a considerable speed.
Both trains were heading south into the city.
The leading train had stopped because it was waiting for another train to leave the Fort Totten station, officials said.
It was unclear why the following train had not received the signal to stop as well, or why the operator did not stop her train manually when she saw the tracks blocked ahead of her, officials said.
Passengers on the second train said it did not slow down at all before impact.
"There was no attempt at braking. We just slammed into whatever we slammed into," passenger Theroza Doshi told Reuters. (Editing by Paul Simao)