The raiders hit the former Amy Johnson School site in the city over the weekend where Keepmoat has just started on a new housing development.

The gang made off with five pallets of scaffolding and used a forklift truck from the site to transfer the pallets on to a getaway vehicle.

Police Sergeant Julian Hart told the Hull Daily Mail: “Metal theft nationally is on the rise and in Hull, we have also been experiencing an increased number of metal thefts from houses, gardens and commercial businesses.

“This is a particularly high-value theft. We are informing scrap dealers about it so they can report any suspicious metal being brought into their premises to the police.

“This tactic has led to a number of arrests in recent months.”

Keepmoat said the theft would not delay work at the site where 140 homes are being built in the first phase, with 600 earmarked for 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.”