CCTV captured one of the culprits using a ladder that was already on site to climb up and dismantle a light and the camera at the LD Nutrition Stadium around 11.30pm last night.
Wearing a black hat and with his face covered by a red or orange mask, he is seen grabbing the camera, bringing the footage to an end.
It is then thought the thieves used a crowbar to force up a roller shutter covering a door and used a brick to smash the bottom section, before crawling through the space.
They then got away with the rugby league club's safe.
It is uncertain how many were involved with the theft, but club spokesman Joseph Crabtree is confident they knew what they were looking for.
He said: "It's an industrial safe and we can't believe it only took two of them to move it. I think it took about seven men to get it in here.
"The computer and anything of any value was left there, they only took the safe.
"There's a mess left for the glass door but that's it, they didn't enter any other rooms."
Meanwhile, police are hoping for information on the theft, and are asking people to contact them on 101 quoting the crime reference number 13180580224.
Alternatively, call Crimestoppers on 0800 555 111.