Blast at Intel's Arizona plant

Seven workers at an Intel Corp microchip manufacturing complex outside Phoenix were injured by a small explosion, fire officials reported, but the company said production was unaffected.

The blast of undetermined origin occurred shortly after 2 pm. local time (4:00 pm EDT/2000 GMT) in a support building at the Intel site in Chandler, Arizona, just southeast of the state capital, said Chandler Fire Department Battalion Chief Brad Miller.

A spokesman for the world's leading chipmaker said the accident site was under construction at the time and that production was uninterrupted.

Miller told Reuters that four workers were taken to local hospitals with injuries ranging from concussions to shrapnel wounds, and three others were treated at the scene for less serious injuries.

He described the incident as both a "small blast" and as a "flash explosion," adding that an automatic extinguishing system quickly doused flames with a mix of water and foam. The extent of damage was not immediately clear.

Early indications were that the explosion occurred inside a chemical storage room of a single-level, 3,000-square-foot (280-sq-metre) building, Miller said. That building and an adjacent structure were evacuated of hundreds of employees, he said.

Miller initially had reported the explosion occurred in a microchip fabrication plant but later said the structure involved was a support building.

A preliminary account of the incident from a company spokesman differed from that furnished by fire officials. An Oregon-based Intel spokesman, Bill Calder, described the incident as a brief fire, not an explosion.

Calder also said a nearby plant and support buildings were evacuated but workers soon returned to the complex and production was unaffected.

The mishap took place at a separate fabrication complex under construction and designed to make Intel's new cutting-edge 22-nanometer chip, due to go into production later this year, Calder said.

Miller said the building where the blast occurred would remain closed while authorities investigated the cause.

"Until we identify everything involved, there's no way we can say when people will be back to work," he said, adding that the 10 other buildings at the site remained open.

Intel's website said its fabrication facilities in Arizona focus primarily on high-volume microprocessor manufacturing.

Shares in the Santa Clara, California-based company were holding steady in after-hours trading.