Police said that arrests were made in the early hours of today based on a complaint by the revenue department under the Thane District Collector.
Senior police inspector T Baravkar of Kapurbawdi police station said that an offence under relevant sections of the Environment (Protection) Rules of 1986 had been registered against 11 persons.
Police said that three persons, who the police identified as contractor Jaggu Khetwani, Usha Rai and one Nitin, are yet to be arrested.
The eight labourers arrested had been hired by the contractor to carry out the destruction of mangroves, police said.