A day before a thunderous explosion that killed at least 15 people at the BP oil refinery in Texas City, Texas, a small fire broke out in the same unit that blew up, officials said on Friday. The company said it was investigating whether the two events were related, but did not yet know. The fire on Tuesday was blamed on a leaky valve in a line in the "isomerisation" unit which boosts gasoline octane and was quickly put out, BP and government investigators said.
"It was in the same general area (as the explosion). It was a leak in a very small plug that either came loose or wasn't in place," said John Bresland of the US Chemical Safety and Hazard Investigation Board.
He told reporters the fire was "probably not connected to the incident the next day," but BP spokesman Bill Stephens said "there's no way to know that."
"We have several comprehensive investigations just getting under way. We're not going to speculate on a relationship between the two, but we'll take a look at everything."
Stephens said the fire was small enough that it was put out with a fire extinguisher and the valve was fixed by replacing a drain plug.
The isomerisation unit exploded on Wednesday less than 24 hours after the fire in a massive blast shook buildings and broke windows for miles around and sent a huge cloud of black smoke billowing into the sky.
Refinery equipment and buildings nearby were levelled, leaving a rubble-filled landscape reminiscent of a war zone at the 1,200-acre complex 35 miles (56 km) south-east of Houston.
Fifteen people died and eight more are in critical condition at area hospitals. At least 100 people were injured, officials said.
Bresland said it was clear to investigators that the blast occurred because there "was a release of a flammable material that caught fire and exploded."
But, he said, "we have yet to determine what the source was."
It was the third fatal accident in a year at the Texas City facility, which is the nation's third largest refinery and produces about 3 percent of US gasoline.
A worker died in a fall last May and two were killed in September when scalding hot water burst from a pipe. An explosion and fire also occurred in March 2004, although no deaths or serious injuries were reported.
On Wednesday, a BP plant operations manager told Reuters there had not been problems at the isomerisation unit.
On Thursday, BP chief executive John Browne told reporters the refinery was "a very safe plant" and he did not think the series of accidents were related, but the company would investigate the possibility.
There have been more than 3,500 accidents at BP's US facilities since 1990, more than any other company, according to a 2004 report by the Texas Public Interest Research Group.
Two Islamist groups claimed responsibility for the explosion in Internet postings on Thursday, but the FBI investigators went to the plant and said they found no evidence of suspicious or criminal activity at the plant.
The Occupational Safety and Health Administration and the chemical board are conducting separate investigations into the explosion. OSHA's probe is expected to take six months, while Bresland said the chemical board will take a year to complete its findings.