A network administrator has locked up a multimillion dollar computer system for San Francisco that handles sensitive data and is refusing to give police the password, the San Francisco Chronicle reported Monday.

The employee, 43-year-old Terry Childs, was arrested Sunday. He gave some passwords to police, which did not work, and refused to reveal the real code, the paper reported.

The new FiberWAN (Wide Area Network) handles city payroll files, jail bookings, law enforcement documents and official e-mail for San Francisco. The network is functioning but administrators have little or no access.

Childs, who remains in custody, is accused of improperly tampering with computer systems and causing a denial of service, said Kamala Harris, San Francisco's district attorney, on Monday afternoon.

"The bail has been set at $5 million, and the exposure in this case if he were convicted on all counts would be seven years in prison," Harris said.

Harris said it's unknown why Childs tampered with the system. The Chronicle, however, reported that Childs was disciplined recently for poor performance. Childs worked in the Department of Technology for San Francisco, making close to US$150,000 a year, the paper reported.

City officials told the paper that Childs may have caused millions in damage while also rigging the network so that other third parties could monitor traffic, posing a huge data security risk. He is also alleged to have installed a tracing system to monitor communications related to his personnel case.

(Robert McMillan in San Francisco contributed to this report.)