A disgruntled city computer engineer has virtually commandeered San Francisco’s new multimillion-dollar computer network, altering it to deny access to top administrators even as he sits in jail on $5 million bail, authorities said Monday.

Terry Childs, a 43-year-old computer network administrator who lives in Pittsburg, has been charged with four counts of computer tampering and is scheduled to be arraigned today.

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The damage is still being assessed, but authorities say undoing his denial of access to other system administrators could cost millions of dollars.

Officials also said they feared that although Childs is in jail, he may have enabled a third party to access the system by telephone or other electronic device and order the destruction of hundreds of thousands of sensitive documents.

Authorities have searched Childs’ home and car for a device that could be used in such an attack, but so far no such evidence has been found.

As part of his alleged sabotage, Childs engineered a tracing system to monitor what other administrators were saying and doing related to his personnel case, law enforcement officials said.