An eyewitness said, on condition of anonymity, that a broken bottle and match box were found at the main gate of the office and it appeared that a bottle filled with petrol was thrown to start the fire.

The police, however, said the cooler pads caught fire because of an electrical short circuit.

Joshi was arrested Thursday in Ghaziabad for her remarks against Chief Minister Mayawati, who termed the statement insulting to her as a woman and a Dalit. Joshi has been charged under the Scheduled Castes and Scheduled Tribes (Prevention of Atrocities) Act.