We are investigating the case and are trying to ascertain the identity of the vandals, police said.
The police have registered a case against unidentified persons who participated in the alleged attack.
Shattered glass were strewn all around the entrance of the building, the police said.
Identities of the vandals and the reason behind the attack have not been ascertained and investigations are on, the police said.
Earlier in the day, Maharashtra Navnirman Sena chief Raj Thackeray had criticised the Maharashtra government for diverting drinking and irrigation water needed by drought-hit farmers, to the Indiabulls power plant, while speaking at a rally in Amravati.
It may be recalled that recently, Bombay High Court had declined a plea by Vidarbha's farmers to recall its March 2 judgement, in which the court had upheld allocation of 87.6 million cubic metres of water annually to Indiabulls' thermal power plant, near the drought-hit region in Maharashtra.