Criminals forced entry to the Lovell site office and stole the keys to pilot houses in the scheme, giving them free access to the buildings and their contents.
A number of new homes were raided and extensively damaged, leaving the developer to face substantial repairs.
Constable Kirsten Young from Broxburn Police Station said: “The developers are obviously incredibly frustrated and disappointed that many of their recently built homes have been targeted and now require considerable repair.
“We believe this damage has been caused by a group of people and would urge anyone who remembers seeing anyone acting suspiciously in the area over the weekend to contact police immediately.
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“Likewise, if you have any other information that you think is relevant to this investigation then please also get in touch.”
The break-ins happened some time between 3pm on Friday last week and 8am on Monday.
Anyone with information should contact Broxburn Police Station via 101 and quote incident number 0637 of the April 29. Alternatively, an anonymous report can be made to the charity Crimestoppers on 0800 555 111.