NEW ORLEANS — Environmental groups put federal officials on notice Thursday that they intend to file legal action to return the Louisiana black bear back to a list of threatened species.

Officials announced removal of the bear from the list in March 2016. Then-Interior Secretary Sally Jewell touted the move, along with various state and federal officials, while visiting the Tensas River National Wildlife Refuge in north Louisiana. Authorities heralded the decision as the culmination of years of work involving federal and state governments, along with private landowners, to protect or restore some 750,000 acres of habitat for the bear.

The Louisiana black bear is one of 16 subspecies of the American black bear. There are an estimated 700 in Louisiana now.

Some conservationists and environmentalists opposed the move when it was announced. On Thursday, the Washington-based Public Employees for Environmental Responsibility released copies of its letter to the Department of the Interior, announcing plans to sue under provisions of the Environmental Protection Act unless the department’s Fish and Wildlife Service restores federal protections for the bear and its habitat. Other groups involved include the Sierra Club’s Delta Chapter and the Louisiana Crawfish Producers Association-West.

The letter says scientific data were neglected when the bear and its habitat were removed from Endangered Species Act protections. It revives issues raised last year by opponents of the “de-listing” of the species. For instance, the environmentalists contend that one area said to be inhabited by Louisiana black bears — the Upper Atchafalaya River Basin — is actually home to a similar Minnesota subspecies introduced to the area in the 1960s.

“The connection of the UARB population with Louisiana black bear populations should not be considered to constitute sufficient recovery, and in fact threatens the remaining Louisiana black bears with hybridization,” the PEER letter said. The letter also states that the Fish and Wildlife Service recovery plan does not adequately provide for “corridors” of forest land connecting different black bear population areas.

Fish and Wildlife Service spokesman Phil Kloer declined comment on points in PEER’s lawsuit notice but said the service stands by the “de-listing” decision.

“We stand by the conservation work of our Fish and Wildlife Service team, the state of Louisiana, private landowners and many other partners whose commitment made this recovery real,” Kloer said in a telephone interview from the service’s Atlanta office.