The Clinton campaign is once again fuming at the FBI after the agency posted a Twitter message on Tuesday advertising a dump of 129 pages of records related to the deeply controversial pardoning by Bill Clinton of a fugitive financier at the moment he left office.

With what seemed like exquisite timing, the agency dropped the documents into the public sphere exactly one week before the election with polls showing a tightening race between Hillary Clinton and Donald Trump.

The action came just four days after FBI Director, James Comey, caused an earthquake in the race for president by announcing steps to examine a huge new trove of emails that may or may not have some bearing on an earlier investigation into Ms Clinton’s use of a private email server.

“Will FBI be posting docs on Trump’s housing discrimination in ’70s?” Brian Fallon, a Clinton campaign spokesperson, asked sarcastically after the latest FBI document release. He added that the timing of the new release appeared “odd”. Demcrats noted that the Twitter account where news of the document release was posted, called ­­@FBIRecordsVault, had been dormant for over a year before being reactivated just on Sunday.

The agency contended that the new documents, which detail what steps were taken to investigate Mr Clinton’s decision to pardon Marc Rich, a fugitive financier who had fled to Switzerland after being convicted of massive tax evasion in the US, were released only in response to a Freedom of Information Act, FOIA, request. Such releases are automated, it said.

But the timing - both of the reactivation of the Twitter account that was used and of the release itself - clearly creates additional doubts about the agency’s commitment to keeping itself out of the political fray and at sufficient distance from the presidential election so as not to influence it, as required by law.

While at first glance there did not appear to be anything fresh in the Marc Rich documents, they inevitably will serve as a reminder of one of the darkest blots on Mr Clinton’s reputation that came at the moment he left office.

The pardon got so much attention because Mr Rich’s wife, Denise Rich, had become a major donor to the Democratic Party and to the Clinton family, giving generously, for instance, to Ms Clinton’s successful 2000 campaign for the US Senate in New York.

The newly disclosed documents made clear, in fact, that within the agency the investigation, which was only wound up in 2005 without any charges being filed, had concerned “possible public corruption surrounding the pardons granted by former president William Clinton.” That is language hardly likely to be helpful to Ms Clinton in the ebbing days of a campaign that has been marked by public distrust of her and her family.

In a statement defending its latest dump-surprise, the FBI said the documents were published after Freedom of Information Act requests and were posted “automatically and electronically to the FBI’s public reading room in accordance with the law and established procedures.” This happens, the statement said, on a “first-in, first-out” basis. Officials added that the agency had been working to upgrade a website in recent months and the completion of that work was the reason the Twitter account had come back to life at the weekend.

The storm created by Mr Comey’s decision to make public the discovery of a new cache of emails possibly pertaining to Ms Clinton’s emailing habits while Secretary of State - they were found on devices belonging to Anthony Weiner, the former Congressman and estranged husband of Clinton top aide Huma Abedin - continues unabated, meanwhile. Democrats have roundly accused the FBI of double standards by declining at the same time to make public any details of work it has done this year to investigate potentially illegal ties between the Trump campaign and Russia.

While there is still no evidence to suggest that the new materials contain anything that would persuade the FBI formally to re-open the investigation into Ms Clinton’s server which it closed in July, it has sent shockwaves through the campaign with Mr Trump using it to double down on his contention that Ms Clinton is “crooked” and deserves to be in jail.

The fall-out for Mr Comey and the FBI is already intense and may last far beyond the election next week.