The club say floodlights, as well as power to the ground's hospitality boxes, scoreboard and turnstiles, have been affected by the theft of electricity cabling.
Tigers chief executive Steve Ferres said: "Our groundstaff returned yesterday (Wednesday) to discover a large amount of cabling had been stolen from the ground. The police have been informed and we will be evaluating the full extent of what needs to be replaced over the next few days."
He added: "Without doubt, it will be a big job and at the worst possible time with the new season fast approaching and our friendly against Featherstone at home only a couple of weeks away.
"We already had a long list of essential repairs that need to be made to the stadium in the coming weeks and this is certainly not going to help our progress.
"To have this setback after a really promising build-up is a real kick in the teeth for us but I am determined not to let it detract from the great work we have already done, as well as the hard work that still needs to be done before the season starts."