A rift has opened between the Obama administration and some of its closest allies - Democratic leaders and environmental organisations - over its refusal to publicly disclose the location of 44 coal ash dumps that have been officially designated as a "high hazard" to local populations.
The administration turned down a request from a powerful Democratic senator to make public the list of 44 dumps, which contain a toxic soup of arsenic and heavy metals from coal-fired electricity plants, citing terrorism fears.
The refusal has put the Obama administration at odds with some of its strongest supporters over an emerging area of environmental concern in America.
Last Christmas, a retaining wall burst on a coal ash pond in Tennessee disgorging a billion gallons of waste and putting pressure on the authorities to bring in safety controls over the management of some 600 similar waste pools dotted across the country.
Some 44 of the most dangerous coal ash dumps are known to be located in populated areas in 26 separate locations. The high hazard designation means that a breach, like the one in Tennessee, could cause death and significant property damage if the sludge spills into surrounding neigbourhoods. But that is all the adminstration will disclose.
"Right now we have a blanket gag order," Barbara Boxer, a California Democrat who heads the Senate environment and public works committee told a press conference last week.
"We are losing what we cherish in America: the citizens' right to know."
Boxer, who has seen the list of sites, said she was only allowed to share the information with fellow senators - not their staff and not local authorities in the affected areas.
"There is a huge muzzle on me and my staff," she said. "They're putting ridiculous restrictions on me."
The local newspaper in Tennessee also ridiculed the decision.
"These waste sites may be environmental and health hazards. But they are unlikely terror targets," said the Knox group of newspapers. "As the muckety-mucks in Washington know, the real danger of disclosure is from angry Americans. If citizens realise they are downstream from fragile mountains of gunk, they will demand action and accountability."
Environmental groups see the gag order on the coal ash sites as a betrayal of Obama's promise, during his speech to staff on his first day in the White House in January, of a new era of openness in government.
"For a long time now, there's been too much secrecy in this city," Obama said in the speech. "That era is now over. Starting today, every agency and department should know that this administration stands on the side not of those who seek to withhold information but those who seek to make it known."
The Environmental Protection Agency under Lisa Jackson has also put emphasis on its moves for greater openness and a greater role for science at the agency - in sharp contrast to the policies under George Bush when government scientific reports were doctored to remove references to global warming.
Lisa Evans, an attorney at Earth Justice which has long campaigned about the potential dangers of the dumps, said environmental organisations were perplexed by the secrecy. "Is this consistent with the way we treat other hazardous sites in this country?" she said. "One Google click will give you the locations of all the nuclear power plants in the US."
Other environmentalists said the Obama administration's failure to disclose the location of the sites was an issue of social justice.
"We know that there are no coal ash sites in Manhattan. So where are these sites?" said Virginia Cramer of the Sierra Club. "They are generally in low income and minority communities, so we are concerned about those communities knowing what types of danger are surrounding them."
An EPA official said the agency was consulting with the US department of homeland security and the army corps of engineers to review the decision.
However, the official said that when it came to revealing the location of the dumps, its hands were tied because of security concerns. Since the 9/11 attacks, the authorities have methodically scrubbed websites listing dams and other structures that could present targets for terrorist attacks. The national inventory of dams now no longer ranks the hazard rating of its structures - although they will list location.
The Obama administration appears to have maintained the policy.
In a letter earlier this month, the army corps of engineers told the EPA to keep the sites secret. "Uncontrolled or unrestricted release [of the information] may pose a security risk to projects or communities by increasing its attractiveness as a potential target," Steven Stockton, the army corps director of civil works wrote.
"It was our attention to release the list, but we certainly feel obligated to take into account any recommendations from our agencies as they release to terrorist attacks," said an EPA official.
"It was very strong language cautioning us from releasing this list."