An environmental group says it is planning a lawsuit over the proposed sale of Plum Island.

The island off of eastern Long Island is home to a federal laboratory that studies dangerous animal diseases.

The Department of Homeland Security, which operates the lab, has announced plans to sell the 840-acre island.

The group Save the Sound said Monday it has filed a notice of intent to sue both the DHS and General Services Administration, which is handling the proposed sale.

Congress has approved plans to build a new laboratory in Manhattan.

The environmentalists say the island is home to endangered bird species that could be threatened if the island is sold.

A DHS spokeswoman referred inquiries to General Services. A spokesman for that agency did not immediately comment.