Work on the Coalfields Highway has been delayed after equipment was vandalised.
Vandals hit the Hamilton Crossing worksite between 4.00pm Monday and 6.00am Tuesday causing more than $10,000 worth of damage.
The offenders have broken into two excavators and two rollers, trashed the inside and released a fire extinguisher in the cabin, completely covering the interior with the extinguisher contents.
They have also significantly damaged a pump at the work site, causing $5,000 worth of damage alone.
Constable Evan Jackson said police are investigating and have seized items they believe may hold forensic value.
"Not only is there a monetary cost, but incidents like this have the potential to delay the completion of the Highway upgrade which affects all of us," he said.
Anyone with any information is asked to call Collie Police Station on 9734 6333.
