Kumar was gheraoed by the Stone Crushers Association members as soon as she reached the district collectorate to attend a meeting for review of development works in her parliamentary constituency, Sasaram, officials said.
They were pressing for her intervention in the revival of the crushing units which have been shut down by the district authorities on the direction of the state government.
The protesters also submitted a memorandum to in this regard.
The Lok Sabha speaker is on a four-day visit to her home district.