A group of around 25 armed Maoists arrived at the crusher plant site and set ablaze eight dumpers, a excavator, pick up van, motorcycle and tractor belonging to the road construction company near Gumhra River on Dumka-Pakur road late last night, Deputy Superintendent of Police B C Ram said.
He said the company was constructing a road under Govindpur-Sahebgunj project aided by Asian Development Bank.
The ultras, however, did not harm any labourers present at the site, he said adding that the security personnel has launched a massive anti-Naxal operation to track down the ultras involved.