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Photos released from the U.S. Chemical Safety Board.

RICHMOND -- U.S. Chemical Safety Board officials said Monday that criticisms would not deter them from communicating with the press, nor had they strained relationships with other agencies in the joint investigation into Chevron's Aug. 6 refinery fire that sent more than 11,000 residents to area hospitals.

"We have a responsibility to the community to provide regular communication," said CSB Chairperson Rafael Moure-Eraso, who toured the site Monday. "It is a priority."

The news conference near Chevron's main gate was the first since news reports exposed an apparent rift between the CSB and Cal/OSHA, a work safety agency. The CSB has held multiple news conferences and given updates to the press, including photos of the site, in contrast to the more taciturn approach of other agencies.

A Cal/OSHA investigator on Aug. 11 posted a statement on his Facebook page ripping the CSB for "grandstanding" and "scaring the public with half-truths."

Cal/OSHA spokesman Peter Melton said his organization is the lead agency among the coalition of investigators, and declined comment on an "employee's personal Facebook page."

Asked whether the recent reports and social media taunts would harm the two agencies' ability to jointly investigate the fire, Moure-Eraso said no.

"We feel like that was the past," he said. "That was a mistake and we must move forward."

CSB Managing Director Daniel Horowitz said the working relationship with Cal/OSHA is "excellent."

"We have certain differences in approach, but we're compatible," Horowitz said.

Investigators still cannot get within 30 feet of the 8-inch diesel pipe that burst Aug. 6, releasing a mammoth vapor cloud that ignited about two minutes later. CSB officials said leaking hydrocarbons and structural concerns continue to keep investigators from reaching the pipe, which will removed and put through a battery of tests.

Horowitz brushed aside questions about what ignited the vapor cloud, emphasizing instead that the focus of the investigation remains why the pipe failed and whether it should have been replaced earlier. Investigators have already interviewed dozens of workers and reviewed thousands of pages of documents.

Meanwhile, Bay Area air quality regulators are investigating whether to add more pollution monitors near refineries in light of the system's poor performance in the Aug. 6 emergency.

While the Bay Area Air Quality Management District and Contra Costa County have mobile monitors to detect gaseous pollutants like sulphur dioxide, the devices do not screen for soot, the suspected cause of the chest, throat and eye irritation that sent thousands of residents to area hospitals.

Contra Costa County Supervisor John Gioia, who chairs the air district's board of directors, said he will propose more monitoring of the Bay Area's five refineries.

"We need accurate and impartial monitoring, and we need it to be paid for by industry," Gioia said.

Contact Robert Rogers at 510-262-2726 or rrogers@bayareanewsgroup.com. Follow him at Twitter.com/roberthrogers. Denis Cuff contributed to this report.