Evidence in the Station nightclub fire case, which Attorney General Patrick C. Lynch last month promised to make public after the nightclub’s owners entered no contest pleas to involuntary manslaughter charges, will not be available until after next month’s election — if ever, according to a letter from the attorney general’s office.

In a Sept. 20 letter to relatives of the 100 people who died in the West Warwick fire, Lynch promised to release evidence “in an attempt to help answer some of your questions” about the fire.

On Sept. 29, the brothers who owned the nightclub, Michael A. and Jeffrey A. Derderian, changed their pleas to no contest to 100 counts of involuntary manslaughter. Michael Derderian, 45, of Narragansett, was sentenced to serve four years in prison. Jeffrey Derderian, 40, of Cranston, was ordered to perform 500 hours of community service. The sentences were part of a plea deal approved by Superior Court Judge Francis J. Darigan over Lynch’s objection.

On Oct. 2, The Providence Journal filed a formal request with Lynch under the state’s Access to Public Records Act for the evidence. Under normal circumstances, public agencies have 10 business days to supply the records or to state why they are exempt from disclosure under the act. Those 10 days expired on Tuesday.

In a letter dated Oct. 11, Lynch’s office invoked a clause in the law that grants an extension “for good cause.”

“Because of the voluminous nature of your request, it is necessary to extend the time to respond an additional twenty business days,” Special Assistant Attorney General Adam J. Sholes wrote in the Oct. 11 letter.

That would extend the time period for a response to Nov. 16, more than a week after Lynch seeks reelection against Republican J. William W. Harsch in the Nov. 7 election.

“We’re committed to the process of getting as much out to the public as fast as we can, but it’s a massive undertaking,” Lynch spokesman Michael J. Healey said yesterday. “He’s not backing off of that commitment.”

Healey said the timing of the election is coincidental. “We didn’t pick the date that The Journal filed its APRA request, nor did we write the law that allows an extension,” he said. “The timing is triggered solely by when we get the request.”

Harsch yesterday blasted Lynch in a statement.

“The cloak of secrecy and deception surrounding the Station Fire Trial has to stop. Mr. Lynch’s attempt to delay the release of vital public information until after the election confirms to me that he has something to hide or someone to protect,” Harsch said. “I believe that the Attorney General’s actions are entirely politically motivated and are an affront to the people of Rhode Island and especially to the victims of the Station Fire and their families. The simple fact is Patrick Lynch doesn’t want the people of Rhode Island to know the truth about the Station Trials. He doesn’t want it known that other individuals should have been prosecuted; and he doesn’t want it known that he agreed to the plea bargain struck in the Derderian trial despite his hollow public objection.”

Harsch’s statement yesterday would seem at odds with comments he made early this month that Lynch should not release the evidence because it would hamper Harsch, if elected, from reopening the case.

Harsch’s campaign coordinator, Thomas D. Shevlin, said yesterday that Harsch still believes the evidence should be kept secret. But, Shevlin said, if Lynch has pledged to make it public, he should do so before the election. Shevlin said that making the evidence public could prevent Harsch from filing charges against additional people or from filing additional charges against the Derderians and a third defendant, rock band manager Daniel M. Biechele, who pleaded guilty to 100 counts of involuntary manslaughter.

Two weeks ago, Lynch’s spokesman Healey said the attorney general expected to file a request that week in Superior Court asking permission to release secret grand jury testimony. Yesterday, Healey declined to say whether the request had been filed, citing grand jury secrecy.

The day after The Journal requested the Station fire evidence, the paper filed a separate request with Lynch for e-mail sent between lead prosecutor William J. Ferland and defense lawyer Kathleen M. Hagerty. The paper hopes those e-mails will shed light on how the Derderians’ plea deal came about. While Lynch objected to the deal at the brothers’ sentencing and has said he never countenanced it, Hagerty has said that Ferland offered the deal with assurances that he had been authorized to do so.

Sholes wrote a reply that, as in the case of the newspaper’s request for the evidence, invokes the 20-day extension.

Healey said that part of the reason for the delay is that Ferland — and other Station fire prosecutors — took vacation time after the case was resolved.