The Iowa presidential caucuses were thrown into chaos late Monday after the state Democratic Party said it found "inconsistencies," delaying results and causing widespread confusion across the state.

The Iowa Democratic Party said early Tuesday that it would release the results of the Iowa caucuses later Tuesday after "manually verifying all precinct results."

Party chair Troy Price said the party is "validating every piece of data we have against our paper trail. That system is taking longer than expected, but it's in place to ensure we are eventually able to report results with full confidence."

The state Democratic party's communications director, Mandy McClure, said on Monday night that there were "inconsistencies" in the reporting of three sets of results. "In addition to the tech systems being used to tabulate results, we are also using photos of results and a paper trail to validate that all results match and ensure that we have confidence and accuracy in the numbers we report," McClure said.

"This is simply a reporting issue. The app did not go down, and this is not a hack or an intrusion. The underlying data and paper trail is sound and will simply take time to further report the results," McClure added.

The state party had earlier said it was carrying out "quality control checks, making sure the numbers are accurate."

The state party hosted a conference call with the campaigns sometime after 11 p.m. ET, but sources confirmed that party leaders hung up as campaign officials pressed for more information about the various reporting issues and when they would receive more data and results. The call became very heated, sources said.

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As the state party scrambled to sift through three sets of numbers, election workers struggled to use a new smartphone app created for caucus organizers to calculate and report results.

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"The app is the issue, and the hotline is smoked," said Joe Galasso, a volunteer in charge of new registrations for Waukee Precinct 2, in Dallas County. A source familiar with the process said the backup phone line was "a disaster."

Another source was more blunt: "The app is f---ing up," said a senior aide to one of the campaigns, who asked not to be identified. "Can't trust the numbers coming in."

Live blog: Follow the latest news and results from the Iowa caucus

Shawn Sebastian, the caucus secretary in Ames, told MSNBC that he’d been on hold on the hotline for about two hours. “They said that they’ll be with me in the order in which you know, I got on hold,” he said, “and there was moment where they did connect for like one second about half an hour ago and then I just wasn’t responsive quick enough and they just hung up on me. So I’m back in line.”

NBC News previously reported that security experts had expressed some concern about the app. The new app — which is supposed to be used in the Nevada caucuses on Feb. 22, as well — first showed signs of trouble earlier in the day, with some precinct leaders and county chairs saying they were unable or unwilling to use it.

The reporting of results was further complicated by new caucus rules that, for the first time, divided the results into three sets:

The "first expression of preference," when caucusgoers pick their favorite candidate.

Vote totals from the "final alignment," when backers of contenders who don't do well have to pick another candidate. "Uncommitted" can be a choice (it won in 1972 and 1976).

The total number of "state delegate equivalents" — the local delegates who will later pick the state's delegates to the Democratic National Convention — won by each candidate.

Some of President Trump's allies capitalized on the delay to sow confusion and doubt. Brad Parscale, campaign manager for the president's re-election bid, tweeted: "Quality control = rigged?"

The delay appeared to rankle some of the campaigns. In a letter to the state party, former Vice President Joe Biden's campaign shredded "considerable flaws" in the night's reporting system.

"The app that was intended to relay Caucus results to the Party failed; the Party’s back-up telephonic reporting system likewise has failed. Now, we understand that Caucus Chairs are attempting to — and, in many cases, failing to — report results telephonically to the Party. These acute failures are occurring statewide," Dana Remus, Biden's general counsel, said in the letter.

In an exchange with reporters, Sen. Elizabeth Warren's campaign manager, Roger Lau, said the delay did not inspire confidence: "Every second that passes sort of undermines the process a little bit."

Shortly after 11 p.m. ET, no results had been reported — a much slower process than had been expected. At about the same time in the 2016 caucuses, roughly 90 percent of the vote had been reported. The party said it would release information about the results as soon as it passes quality control, adding that it was taking additional steps out of an abundance of caution.

"What we know right now is that around 25 percent of precincts have reported, and early data indicates turnout is on pace for 2016," McClure said.