It's entirely up to the investigators themselves. They have to take whatever circumstances they have and come to their own determination on whether this is something that they believe has been an offence or not. That could be from visiting the property and from seeing the type of damage that has been done.
The intention is always to corroborate. Police cannot necessarily advance an investigation without trying to corroborate whatever information has already been received, or whatever information they are receiving. It would be up to that investigator to take the steps necessary to try to corroborate whatever statement they're receiving from a victim or a potential victim.