One of the more gruesome tasks for the police and railway workers picking through the ash and carnage today at the scene of London's latest commuter-train crash involved collecting cellular phones strewn around the wreckage. Officers pushed the "redial" button to contact the last person called and then asked those who answered if they had a friend or relative on either of the two mangled trains.

That was just one of the methods police used as they struggled to identify victims of the fiery collision between the trains just west of London's Paddington Station at 8:11 Tuesday morning. As families across southwestern Britain waited at home for the dreaded telephone call, police reported that at least 70 people died in the accident and estimated that the final death toll could pass 100.

The toll is still uncertain because it has been impossible thus far to recover dozens of bodies presumed to be buried in the metallic rubble. In addition to the 28 bodies retrieved, police said 42 people known to have boarded the trains have not been located and are presumed to have died.

Beyond that, Scotland Yard says it has been told of another 100 or so people who are unaccounted for and may have been on one of the trains. Any who were aboard almost certainly died in the intense firestorm that engulfed both trains within minutes of the crash. Temperatures inside the most severely burned car may have reached 1,000 degrees centigrade, police said, after the diesel fuel tanks on both engines burst and ignited.

Amid the confusion and anguish over the unidentified victims, an angry political argument arose about the safety of Britain's recently privatized rail network, which carries millions of passengers every day. The union representing train drivers threatened a nationwide strike next week unless immediate safety improvements are made.

Railtrack, the company that owns the nation's tracks and rail signals, said today that the accident occurred when one of the trains--heading west out of London--raced past a red danger signal about two miles northwest of Paddington. The same error--and, in fact, the very same signal--was blamed for Britain's last major rail crash, which occurred on the same stretch of track in 1997. Reports emerging today indicated that several other train drivers have missed the same red signal in recent years, and they have complained that it is hard to see.

Emergency workers made little progress today in finding victims, mainly because they have not yet been able to set up heavy lifting equipment at the crash site, in the Ladbrook Grove neighborhood of West London. Accordingly, police tried other means of identifying victims. They searched for rings, purses, papers, snatches of clothing--and cellular phones.

At stations along the route of the train that was heading into London, police were checking license numbers of cars left overnight in parking lots, on the theory that they may have been left there Tuesday morning by passengers who died in the crash.

Police said they have received more than 5,000 phone calls from people worried that friends or relatives were on the trains. Police have tried comparing the names of those reported missing with those of passengers known to have survived, but many survivors--primarily those on rear cars--walked away essentially unscathed without reporting to police.

The crash involved a multi-car express train run by Great Western Trains, which carries about 500 passengers daily into London from Cheltenham, Reading and other southwestern commuter towns, and a shorter train run by Thames Trains, with an estimated 100 passengers aboard.

As the Great Western express raced eastward toward Paddington at about 50 mph, the Thames train left Paddington heading west toward Bedwyn. Railtrack officials said today that the Great Western train had a green signal to take the main line into the station, but the Thames train, passing two yellow warning signals and the red danger signal, curved onto the main line just as the Great Western train reached the crossing. The Thames train smashed into the Great Western express, knocking the engine and the first passenger car off the track and igniting the fuel tanks.

"We heard a huge bang, then everything went dark, and we all went flying," Stuart Allen, a passenger on the Great Western train, told the BBC. "Then bang! And bang again, and we started to see flames. So just when you realized you have survived the crash, the fear became the fire."

But despite the horror of the moment, the famous British stiff upper lip was firmly in place at the accident scene. One of the passengers on the inbound train was novelist Jilly Cooper, who was on a rear car and emerged unhurt. In an interview with Sky News, Cooper said that in the aftermath of the accident: "I was proud to be British. Everyone was so calm. The rescue teams went about their business, and those of us who could do just walked quietly away."

The Times newspaper boasted in a large headline that the "British displayed 'grace under pressure.' "

CAPTION: Accident investigators inspect the shredded wreckage of two passenger trains that collided Tuesday near Paddington rail station in central London.