(CNN) - BuzzFeed says its sources are "standing behind" the bombshell report about the special counsel investigation.
"We're being told to stand our ground. Our reporting is going to be borne out to be accurate, and we're 100% behind it," investigative reporter Anthony Cormier told CNN's Brian Stelter on "Reliable Sources" Sunday.
Cormier was joined by BuzzFeed editor-in-chief Ben Smith on "Reliable."
The pair defended a story published on Thursday that said President Donald Trump directed his longtime personal lawyer Michael Cohen to lie to Congress about a potential hotel construction project in Moscow. The information was attributed to two unnamed "federal law enforcement officials" involved in the investigation.
Cormier, who wouldn't reveal his sources when asked, said the story had been in the works for months and went through a "rigorous" vetting process. The story was reviewed by at least three editors, Smith said.
But Special Counsel Robert Mueller's office, which is investigating Russian interference in the 2016 presidential election, including any links or coordination between the Russian government and individuals associated with the Trump campaign, took the extraordinary step of issuing a statement that challenged the accuracy of the report, but didn't provide details.
"Buzzfeed's description of specific statements to the Special Counsel's Office, and characterization of documents and testimony obtained by this office, regarding Michael Cohen's Congressional testimony are not accurate," Peter Carr, a spokesperson for Mueller's office, said in a statement that came out hours after BuzzFeed's story was published.
Smith said BuzzFeed is "eager" to understand which parts of the report Mueller's office is challenging as inaccurate. He said BuzzFeed reporter Jason Leopold, who coauthored the story, submitted a Freedom of Information Act request for details on how the statement from Mueller's office was constructed.
Stelter on Sunday also pressed Cormier and Smith on whether BuzzFeed had done enough to seek comment or guidance for the story from Mueller's office before publishing the report.
Leopold, who has a checkered reporting past, sent an email to Carr, Mueller's spokesperson .
"Anthony [Cormier] and I have a story coming stating that Michael Cohen was directed by President Trump himself to lie to Congress about his negotiations related to the Trump Moscow project," the email read. "Assume no comment from you but just wanted to check."
Carr replied, "Thanks, Jason. We'll decline to comment."
The Washington Post reported Saturday that Mueller's office was then blindsided by details in the BuzzFeed report, including the assertion that Cohen told the special counsel that Trump instructed him to lie to Congress.
Stelter said he thought Leopold's email was a "shockingly casual" way to request comment for such an explosive report.
"There's a dereliction of duty to send a three-sentence email for comment," Stelter said.
He added that for major stories, it's customary for reporters to send sources a detailed list of the facts that the reporter planned to include.
Smith said that he thought Leopold's email stated "the heart of the story" and added that BuzzFeed has for months been at the forefront on reporting about Trump's business ties to Moscow.
"It has not been our experience that the special counsel is forthcoming with information," Smith said.
Journalist Carl Bernstein, a CNN political analyst, told Stelter on Sunday that he thought it was "going to take time before we fully understand what the exact truth is here."
"We don't know where we are with this story right now," he said.
Bernstein defended coverage of the BuzzFeed report by other news organizations. "We had to report it and attribute it to BuzzFeed, and as I said on our air, we don't know whether or not this story is accurate, contextual, true, and it needs to be run down," he said.
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