Militants in Iraq have attacked a key oil pipeline between the northern Iraqi city of Kirkuk and the port of Ceyhan in Turkey.
Insurgents have repeatedly attacked Iraq's oil infrastructure
The explosion was caused by an improvised device placed next to the pipeline near the northern town of Bayji, a US military official said.
The blast triggered a major fire that spread to a nearby construction site.
A security official at the state-run Northern Oil Company played down the effects of the attack.
He told the AP news agency that the pipeline had not been affected by the blaze.
Insurgents in Iraq have repeatedly attacked the country's oil infrastructure in a bid to undermine the
interim government and deprive it of money for
The authorities limited exports through the northern pipeline that runs to Turkey several months ago as a result.
While the northern oilfields are one of Iraq's most important resources, the country relies almost entirely on the southern oilfields for its income, says the BBC's Peter Greste in Baghdad.
Some 1.8 million barrels of oil a day flow through the country's offshore terminals, earning Iraq around $1bn a month over the past year.
So far no big attack has succeeded, but security analysts warn that the infrastructure is still hugely vulnerable.
Tuesday's attack came as oil prices in Europe reached a 14-year high amid fears about the security of supplies. London Brent Crude was selling at well over $40 a barrel.