Valley Center ? Federal investigators plan to return to Washington today to assess preliminary data and interviews regarding the July 17 explosion at a solvent plant here.

The investigation by the U.S. Chemical Safety Board, an independent federal agency charged with investigating industrial chemical accidents, is focusing on Barton Solvents’ storage tank and transfer areas and its practices on handling flammable materials, said lead investigator Randy McClure.

The agency is also looking at relevant federal, state and local regulations on flammable material handling and storage, McClure told reporters.

Investigators are looking at the possibility that static electricity ignited flammable vapors inside a tank, causing it to rocket out of the plant boundaries, landing about 50 feet away, he said. The ensuing fire rapidly engulfed the area, causing other tanks to overheat and explode.

Two tank tops, each 10 feet in diameter, landed outside the plant, including one that struck a nearby house. A nearby business also suffered minor damage after it was struck by a flying tank vent valve.

“The CSB believes that this incident posed a serious potential for injury to plant employees and the neighboring community and will continue to collect and analyze evidence that will help us more conclusively identify the causes of this explosion and fire,” McClure said.

He cited the off-site debris, the large flames, the smoke that drifted across the community and the vapor release as serious health concerns.

“There were lot of potential threats to the community,” McClure said. “It is not just jargon on our part. We really consider it a serious threat to the community.”