The break in occurred on a housing development at the former Amy Johnson School site, according to the Hull Daily Mail.
The thieves escaped with five pallets of scaffolding and siphoned diesel from vehicles.
Police believe a forklift truck from the site was used to lift the pallets on to their getaway vehicle.
Some 600 homes are planned for construction on the site.
A Keepmoat spokesman said: "The site does have a security presence at all times. Someone is there 24/7.
"But it is a large site. We are having a look at the security arrangements in light of what has happened.
"Although it has been an inconvenience, this theft will not affect the building programme."
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