An alliance of environmental groups has welcomed reports that detainees have been moved from Florida’s notorious “Alligator Alcatraz” immigration jail, but have promised to press ahead with legal action to ensure its permanent closure and the restoration of the fragile Everglades wetlands where it is located.

The Department of Homeland Security (DHS) said in a statement late on Tuesday that Immigration and Customs Enforcement (ICE) and authorities in Florida “have moved illegal aliens from the soft sided facility [and] transferred them to other facilities” for their safety, citing this month’s beginning of the Atlantic hurricane season.

But despite reports last month that the closure of the detention facility was imminent, neither the DHS or state officials have confirmed any plans. An observer at the remote site on Wednesday said buses apparently carrying detainees continued to come and go, while supplies, including jet fuel, were still being delivered.

About 22,000 undocumented immigrants have passed through the jail since it opened last July, Ron DeSantis, Florida’s Republican governor, said last month.

At a press conference on Wednesday, plaintiffs in a lawsuit seeking the jail’s closure and full restoration of the site say they will return to district court in Miami this month in pursuit of their goals, citing the “lack of transparency” by the DHS.

“We don’t know what they’re doing, but we think the judge is going to get to the bottom of it and get definitive answers about what their long-term plans are,” said Paul Schwiep, an attorney representing groups including Friends of the Everglades, the Center for Biological Diversity and the Miccosukee Tribe of Indians.

“We’re not going to be done until the lights are off, the fences are down, the tents are gone and there’s a commitment that it will not be rebuilt.”

Eve Samples, executive director of the Friends of the Everglades, said she was skeptical of the DHS statement.

“If we’ve learned anything over the past year, it’s that we can’t take the government officials involved in this project at their word,” she said.

“If this is indeed true, it is welcome news, but the harm is continuing.”

Elise Bennett, Florida and Caribbean director and attorney at the Center for Biological Diversity, said continued judicial scrutiny of the detention center was crucial. DeSantis, she said, bore responsibility for environmental damage caused when the jail was hastily constructed by the state and pressed into service as a government detention and deportation facility last summer.

“If there are truly no more people detained at the facility, that’s a significant milestone, but it’s not the end of the matter for us,” she said.

“We’re not going to let the Trump and DeSantis administrations quietly distance themselves from Alligator Alcatraz and pretend it never happened. Diesel generators are running around the clock, spewing air pollution into [the] Big Cypress [national preserve], surrounding communities and the Everglades.

“A number of these generators are running lights 24/7 that continue to blaze into the night sky, degrading and destroying night-time foraging habitat for endangered Florida bonneted bats and Florida panthers. And we know 20 or more acres of new paving is contributing to unmitigated polluted storm runoff into the surrounding wetlands.

“We are committed to ensuring the full and final closure of the detention camp and a complete restoration of Big Cypress for the people and the rare and endangered species who depend on this place.”

The lawsuit is set to resume later this month before Miami district court judge Kathleen Williams, who issued a preliminary injunction ordering the closure of the detention center last year. Her ruling was reversed by a three-judge appeals panel that included the wife of a lawyer whose company earned millions of dollars working for the DeSantis administration.

Schwiep said the alliance would press ahead with its demand for a permanent order for closure of the jail, to which DeSantis committed hundreds of millions of dollars of taxpayers’ money, much of it taken from state emergency preparedness and response budgets.

“They built a secret gulag in the Everglades without even pulling one permit, without conducting any environmental review, without complying with environmental law, and now they hope that they can slink away in the middle of the night without explaining to anyone what they did, why they did it or how they proposed to clean up the messes they’ve made,” he said.

“We don’t intend to let them get away with it.”

Separately, an immigration advocacy group that has hosted vigils at the jail every Sunday since it opened last summer criticized the DHS for claiming the 1 June start of hurricane season was the reason for moving the detainees.

“As Floridians will remember, Alligator Alcatraz was opened during hurricane season last year, so their belated concern for the welfare of people detained there, people they have shackled and put in torture boxes, denied medical treatment, pepper-bombed, given rotten food, strains credulity,” said Noelle Damico, director of social justice for the Workers Circle.

“Through 47 consecutive weeks of public protest, testimony in Congress, conscience-shocking press coverage and pressure on lawmakers, thousands upon thousands of people have made it politically toxic to continue operations; its moral and financial cost are too high.

“We will verify their claim that all people have been moved and through our legal partner, Sanctuary of the South, we will provide free legal counsel to people wherever they land, and keep the pressure on until Alligator Alcatraz is shut down for good.”