An American missile, identified from the remains of its serial number, was pinpointed yesterday as the cause of the explosion at a Baghdad market on Friday night that killed at least 62 Iraqis.
The codes on the foot-long shrapnel shard, seen by the Independent correspondent Robert Fisk at the scene of the bombing in the Shu'ale district, came from a weapon manufactured in Texas by Raytheon, the world's biggest producer of "smart" armaments.
The identification of the missile as American is an embarrassing blow to Washington and London as they try to match their promises of minimal civilian casualties with the reality of precision bombing.
Both governments have suggested the Shu'ale bombing and the explosion at another Baghdad market that killed at least 14 people last Wednesday were caused by ageing Iraqi anti-aircraft missiles. Jack Straw, the Foreign Secretary, said yesterday it was "increasingly probable" the first explosion was down to the Iraqis and Peter Hain, the Welsh Secretary, suggested on BBC's Newsnight last night that President Saddam sacked his head of air defenses because they were not working properly.
But investigations by The Independent show that the missile thought to be either a Harm (High Speed Anti-Radiation Missile) device, or a Paveway laser-guided bomb was sold by Raytheon to the procurement arm of the US Navy. The American military has confirmed that a navy EA-6B "Prowler" jet, based on the USS Kittyhawk, was in action over the Iraqi capital on Friday and fired at least one Harm missile to protect two American fighters from a surface-to-air missile battery.
The Pentagon and Raytheon, which last year had sales of $16.8bn (Â£10.6bn), declined to comment on the serial number evidence last night. A US Defense Department spokeswoman said: "Our investigations are continuing. We cannot comment on serial numbers which may or may not have been found at the scene."
An official Washington source went further, claiming that the shrapnel could have been planted at the scene by the Iraqi regime.
On Saturday, Downing Street disclosed intelligence that linked the Wednesday attack and by implication Friday's killings on Iraqi missiles being fired without radar guidance and falling back to earth. The Prime Minister's spokesman said: "A large number of surface-to-air missiles have been malfunctioning and many have failed to hit their targets and have fallen back on to Baghdad. We are not saying definitively that these explosions were caused by Iraqi missiles but people should approach this with due skepticism."
The Anglo-American claims were undermined by the series of 25 digits and letters on the piece of fuselage shown to Mr Fisk by an elderly resident of Shu'ale who lived 100 yards from the site of the 6ft crater made by the explosion.
The numbers on the fragment retrieved from the scene and not shown to the Iraqi authorities read: "30003-704ASB7492". The letter "B" was partially obscured by scratches and may be an "H". It was followed by a second code: "MFR 96214 09."
An online database of suppliers maintained by the Defense Logistics Information Service, part of the Department of Defense, showed that the reference MFR 96214 was the identification or "cage" number of a Raytheon plant in the city of McKinney, Texas.
The 30003 reference refers to the Naval Air Systems Command, the procurement agency responsible for furnishing the US Navy's air force with its weaponry.
The Pentagon refused to disclose which weapon was designated by the remaining letters and numbers, although defense experts said the information could be found within seconds from the Nato database of all items of military hardware operated across the Alliance, "from a nuclear bomb to a bath plug", as one put it.
Raytheon, which also produces the Patriot anti-missile system and the Tomahawk cruise missile, lists its Harms and its latest Paveway III laser-guided bombs, marketed with the slogan "One bomb, one target", as among its most accurate weaponry.
The company's sales description for its anti-radar missile says: "Harm was designed with performance and quality in mind. In actual field usage, Harm now demonstrates reliability four times better than specification. No modern weapons arsenal is complete without Harm in its inventory."
Faced with apparent proof that one of its missiles had been less accurate than specification, Raytheon was more coy on the capabilities of its products. A spokeswoman at the company's headquarters in Tucson, Arizona, said: "All questions relating to the use of our products in the field are to be handled by the appropriate military authority."
Defense experts said the damage caused at Shu'ale was consistent with that of Paveway or, more probably, a Harm weapon, which carries a warhead designed to explode into thousands of aluminum fragments and has a range of 80km.
Despite its manufacturer's claims, it also has a record of unreliability when fired at a target which "disappears" if, as the Iraqi forces do, the target's operators switch their radar signal rapidly on and off. Nick Cook, of Jane's Defense Weekly, said: "The problem with Harms is that they can be seduced away from their targets by any sort of curious transmission. They are meant to have corrected that but there have been problems." During the Kosovo conflict four years ago, a farmer and his daughter were badly injured when a missile exploded in their village. A shard of the casing was found near by with a reference very similar to that found in Baghdad: "30003 704AS4829 MFP 96214."
The American navy confirmed that one of its Prowler jets, which is used to jam enemy radar, had been over an unspecified area of Baghdad on Friday night. A pool reporter on the carrier USS Kittyhawk was told that the Prowler squadron had fired its first Harm on Friday evening in response to an air-defense unit that was threatening two F/A-18 Hornet jets. Lieutenant Rob Fluck told the journalist that the crew had not seen where their missile had landed.