HAMPTON, N.H. — Authorities are looking for volunteers to help clean up hundreds of thousands of small plastic disks swept downriver from a wastewater treatment plant to the shores of New Hampshire and Massachusetts.

The 2-inch-wide disks covered with mesh screens came from the Hooksett plant, where they were used in tanks to promote growth of bacteria that feeds on waste. A week after heavy rain carried them into the Merrimack River on March 6, the disks started appearing along the river and on the beaches in Hampton and Seabrook, N.H., and Salisbury, Newburyport and Amesbury, Mass.

The disks are not hazardous waste and pose little health risk, said Jim Martin, spokesman for the New Hampshire Department of Environmental Services.

Preliminary tests done on disks in both states found no E. coli bacteria contamination, though someone who touched the disks with bare hands and then put their fingers in their mouths might experience abdominal pain, vomiting or diarrhea, he said.

Martin said people should wear gloves while picking up the disks, which can be disposed of in landfills as solid waste, and wash their hands thoroughly afterward. But there’s no reason for the public to be alarmed, he said.