Minnesota added another 140 COVID-19 deaths to the state's toll on Tuesday, including 138 that were only confirmed after identifying four labs that hadn't been disclosing test results as required.

About 37,000 test results were not reported to the Minnesota Department of Health over the past five months by the labs, including 891 positive COVID-19 test results, all long-term care residents.

The missing results were discovered by state health officials after they determined that there had been no corresponding lab reports for cases that had been identified by long-term care facilities as well as through death certificates.

"This is a situation in which labs did not follow the law and we did not get reporting," said state infectious disease director Kris Ehresmann.

State epidemiologists routinely conduct audits of public health data, but the surge of cases, hospitalizations and deaths last fall created delays.

"We did not have the capacity to do the usual follow-up and data quality assessment," she said.

The increase of backlogged infections and deaths brought Minnesota's total in the pandemic to 6,696 COVID-19 deaths and 492,108 diagnosed infections with the novel coronavirus that causes the infectious disease.

Without the backlog, Minnesota health officials would have reported 750 new cases and two deaths on Tuesday.

State health officials require that death certificates that list COVID-19 complications as a cause of death be confirmed by a positive test result.

"In order for a death to be reported by us it has to be validated and confirmed," Ehresmann said.

State Health Commissioner Jan Malcolm declined to identify the four labs that failed to meet Minnesota's reporting requirements because of an ongoing investigation that could result in administrative fines and penalties.

An investigation has been launched to learn why the labs fell short on reporting. The labs face a maximum $10,000 fine if investigators find rule violations and could also be subject to federal action.

Malcolm said a reminder was being sent to all labs this week about the reporting requirements.

Minnesota has 924 labs processing COVID-19 test results, compared with 161 labs typically processing seasonal influenza test results.

Ehresmann said the lack of reporting by the four labs did not result in any delay in care or mitigation measures, because the long-term care facilities had become aware of their outbreaks separately.