The Canal and River Trust has been accused of a cover-up after it released heavily-censored reports about a dam which partially collapsed.
Residents in Whaley Bridge, Derbyshire, were evacuated amid fears Toddbrook Reservoir would burst and flood the town.
The trust released inspection reports with large sections blacked out, citing concerns over national security.
But critics said they believed this was just an excuse.
People in the town spent almost a week away from home when part of the dam’s auxiliary spillway collapsed in August.
The reservoir and dam were inspected by the Canal and River Trust in November 2018, and separately by an independent inspecting engineer.
Residents have previously raised concerns about the condition and maintenance of the reservoir and dam, after photos emerged of vegetation growing from the spillway.
Both reports were sent to the BBC and others following Freedom of Information (FOI) requests.
Large sections of the copies received by the media contained large blacked-out sections.
Matthew Forrest, who has been among a group of residents to have called for a public inquiry and criminal investigation, said the redactions seemed “ludicrously heavy-handed”.
“The population of Whaley Bridge had very little confidence in the Canal and River Trust as things stood after the near disaster in August that could have potentially killed thousands of people,” he said.
“This nonsensical black hole of a document does little to build upon any remaining confidence and faith in the Canal and River Trust to internally investigate the causes, let alone replace the neglected Toddbrook Dam.”
Information left in the Canal and River Trust report includes dates when the reservoir was inspected, but measures that were taken “in the interests of safety” and “matters specified to be watched by the supervising engineer” have been redacted.
The independent report includes a description of the reservoir and the geology of the area, but even parts of these sections have been redacted.
The trust said it had redacted information on the basis of “national security and public safety”.
There was “a high level of public interest in not releasing information that would result in a threat to public safety”, it said.
‘Acts of sabotage’
“If the trust were to release copies of these reports, which were not redacted, it would be releasing key details of the infrastructure and potential vulnerabilities of the Toddbrook Reservoir.
“This would prejudice the protection and safety of the public through potential damage or disruption to the national infrastructure by acts of sabotage.”
In response to accusations of a cover-up, the trust said: “We are following the regulator’s – the Environment Agency’s – policy on any disclosure given the sensitive nature of inspection documents.
“For security and safety reasons, they don’t release information that could expose a vulnerability with a reservoir.”
The BBC has challenged the Canal and River Trust’s FOI response after being advised it appeared the trust had redacted material not related to public safety.
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Residents have pointed out that the reservoir has been drained, which meant there would be no flood risk even if someone was to sabotage it.
“Surely they [CRT] must have realised the farcical nature of distributing a 90% blacked out report?” Mr Forrest said.
“Some may speculate that they have done it in order to quash any further inquiry.”