Executions in California will remain suspended after a state appeals court ruled that corrections officials made several "substantial" procedural errors when they adopted new lethal injection rules.

The 1st District Court of Appeals said the California Department of Corrections and Rehabilitation failed to explain, as required by state law, why it was switching from a three-drug injection method to a single drug.

The court's opinion, which affirmed a lower court ruling, also said the agency misled the public by not providing the documents and information it used to reach its decision.

Corrections spokeswoman Deborah Hoffman said in an email that the agency was reviewing the ruling.

"In the meantime, at the governor's direction, CDCR is continuing to develop proposed regulations for a single-drug protocol in order to ensure that California's laws on capital punishment are upheld," Hoffman said.

California has not executed an inmate since 2006, when a federal judge halted the practice, finding that the three-drug mixture amounted to cruel and unusual punishment. The state was ordered to redo its capital punishment system.

Since then, California has built a new death chamber at San Quentin State Prison and trained a new team to carry out executions.