Last Sunday week, cables and equipment were damaged and stolen from a plant room near the Casey Indoor Leisure Complex, which houses Cranbourne library, radio station 3SER and KC Indoor Sports Centre.

A power spike, believed to have been triggered by the theft and vandalism, caused 3SER to go off the air for five hours, and the library and the indoor sports centre to close on Monday.

Mike Allday, director of the indoor sports centre, said last Thursday the centre's lights caught fire and a security system, computers, cash registers and fridges were destroyed. His early damages bill estimate was $30,000.

"[The power spike] bypassed our safety switches. It was such a high voltage in a short time. We went to open to trade on Monday and we didn't know what was going on."

At the library, 22 computers in the public and administration wings were damaged, disabling public internet services until computers are replaced.

Casey Cardinia Library Corporation chief executive Peter Carter said library records were unaffected, with most computers connected to other circuits and shielded by anti-surge protection. The library was closed on Monday afternoon while the affected power circuits were repaired.

Leisure complex co-tenants the Cranbourne U3A, Turningpoint Family Church, Bowland Cranbourne and Balla Balla Community Centre escaped the power spike unscathed. Duncan Turner, acting building manager for the City of Casey, which owns the leisure complex, said the damage cost was still being assessed.

Casey Mayor Lorraine Wreford urged witnesses or people with information to contact police.

Information to Crime Stoppers on 1800333000.