In Syria, the dust settles, the story holds

A British engineer says an overinflated tyre could have caused a deadly explosion in Damascus.

The wreckage of an Iranian pilgrims' bus after an explosion last week on the outskirts of Damascus.

DAMASCUS // If you read, watched or heard any of the recent news reports out of Syria, you probably know that Sunni extremists set off a bus bomb in the Shiite neighbourhood of Saida Zeynab on Thursday, killing at least three people and raising fears of rising sectarian tension.

The Syrian authorities denied the explosion was a bomb, but ironically explained the fatalities had been caused by an "overinflated tyre". The various news reports naturally mentioned this denial, but did so in a way that made it clear nothing of the sort could have been true. Photographs of the damaged coach, the windows smashed, its side torn and blackened from fire, emphasised the point this was not the result of an accidentally popped tyre.

The only problem with all of these accounts is that there may not have been a bomb after all. The explosion, in fact, could well have been caused by an overinflated tyre. "It's well known within the industry for people to be killed from over inflating tyres," explained a senior engineer at a leading tyre manufacturer in the UK. He spoke on condition of anonymity because his company, a global brand that makes tyres for cars, lorries and aircraft, did not want its name associated with a fatal incident it had not been involved in.

The engineer, who said he had heard of the Damascus explosion, stressed it was impossible to know with certainty what had taken place without visiting the site. But, he said, tyre explosions could be extremely powerful. "Coach or lorry tyres are not like those on cars," the engineer said. "They have plies inside them, metal reinforcement that lets them keep their shape. And you put a lot of pressure in these tyres, say 90 pounds per square inch, that's three times more than a car, it's a lot of pressure.

"If you put too much air in, or if the tyre is old and weak and not properly maintained, it can explode, and those metal plies are probably going to go flying." Eyewitnesses to the explosion reported hearing a bomb go off, something the engineer thought could well have been a tyre. "A lorry tyre bursting at 120 PSI [pound-force per square inch] or something makes a hell of a bang; it sounds like a bomb," he said.

Thursday's blast left parts of the bus badly damaged, its windscreen smashed and engine burned. A van some 15 metres away had a piece of shrapnel-like debris punched through its window and there were three confirmed deaths. However, while significant, the scale of destruction did not measure up to that caused by the car bombings so common in neighbouring Iraq; those bombs sometimes throw heavy engine blocks 30 to 50 metres, blow craters into concrete roads or demolish the walls of surrounding buildings. Windows in the immediate vicinity get broken.

When the Syrian security forces finally allowed journalists onto the blast site in Saida Zeynab, it was clear there was no crater. A taxi parked alongside the coach, on the same side as the explosion, had some of its windows smashed, but not all of them. There was even some unbroken glass in the immediately adjacent tyre workshop. And the coach itself, while damaged, was far from torn to pieces. Most of the bodywork was intact, the engine and chassis appeared to be in place, even the seats above the site of the explosion, while misshapen, were still there.

Fire damage was significant but, in light of the British tyre engineer's comments, it seems possible that flying metal debris could, for example, have punctured the fuel tank or fuel lines resulting in a blaze. Under those circumstances, the claim that the explosion came from a burst tyre does not sound so ridiculous as it undoubtedly does at first glance. Given the scale of damage, if it had been a bomb, it appears to have been a small one, perhaps of the kind used in assassinations in Iraq, when the killers do not want to inflict mass casualties.

If it were that type of bomb, however, it is unclear why it was apparently placed near the engine compartment and right-side rear wheels - clearly the area where the blast had its origins. Surely any bomb, large or small, would more likely have been placed in the luggage bins underneath the bus or inside a bag in the passenger compartment. A more important question is why would any Sunni militant detonate the bomb in a petrol station when, five minutes drive away, is the Sayda Zeynab shrine, always densely populated with Shiite pilgrims?

As reporters waited at the blast site, the Syrian interior minister, Saeed Sammur, arrived. The presence of such a senior official only added to the sense it must have been a bomb - government ministers are not usually dispatched to the scene of industrial accidents. Yet Mr Sammur only turned up after it was already an international incident. By that time satellite news channels - including Iranian state-controlled media - had long been in overdrive, saying there had been a bomb and that Iranian pilgrims had been killed. Perhaps the Syrian government decided a senior figure should be dealing with such a high-profile matter.

That Saeed Jalili, Tehran's chief nuclear negotiator and secretary of Iran's Supreme National Security Council, was visiting Syria on the same day only added to the sense of symmetry and crisis. It was hardly mentioned in news reports that he was miles away from the blast. The implied connection hung on the airwaves: this was an effort by Sunni militants to damage Syrian-Iranian ties. A growing number of media outlets and commentators rushed to speculate that this must be a sectarian conflict. There was talk of "destruction", "these militants" - as if the bombing had been confirmed - and even a wild suggestion Syrians felt themselves about to be enveloped in "carnage".

Syria's public relations machine did little to tamp down the hysteria. Their spokespeople briefly mentioned an overinflated tyre, offered no extra details and summarily dismissed any further questions. One critical point the speculative stories failed to address was just why the Syrian authorities would claim a bombing had been an accident. Syria repeatedly justifies its harsh suppression of all internal dissent on the grounds of a domestic threat from violent Islamic extremists. A bomb would fit that narrative perfectly, whereas a blown tyre does not.

Thursday's explosion might well have been a militant attack, as was widely implied. But, utterly implausible as it may at first sound, there are reasons to believe the Damascus bomb of December 3 may not have been a bomb at all. [e-mail]