Returns from the Iowa presidential caucuses were slower than expected on Monday night as the state Democratic Party said it had found "inconsistencies" in the reporting of results and some election workers encountered issues with a results app, NBC News reported.

In fact, a source in the Democratic party told The Hill, "We do not expect results tonight."

"We found 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," state party communications director Mandy 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," she added.

McClure said there was no timetable for when the results would be published.

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

For the first time, the state Democratic Party will report three sets of results: "the first expression of preference" from caucusgoers for a candidate; vote totals from the "final alignment" after backers of lower-ranking contenders make their second choice; and the total number of state delegate equivalents won by candidates.

"The integrity of the results is paramount. We have experienced a delay in the results due to quality checks and the fact that the IDP is reporting out three data sets for the first time," McClure explained.