SAN FRANCISCO (AP) -- California regulators have ordered Pacific Gas & Electric Co. to lower the pressure on some natural gas pipelines in heavily populated areas to 20 percent below their maximum thresholds.

The California Public Utilities Commission directed PG&E on Wednesday to drop the pressure on pipelines located in the Central Valley, Santa Clara County and the Santa Cruz County coast. The order stemmed from its investigation into the Sept. 9 explosion in San Bruno that killed eight people and destroyed 38 homes.

PG&E said late Wednesday that it already has started lowering pressure on the lines below their maximum allowable operating pressures.

The company also acknowledged it had intentionally increased the pressure on a dozen pipelines temporarily, in some cases going above the limit "by a few pounds."

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