Large group COVID-19 outbreaks remain a concern in Minnesota ahead of school reopenings that could accelerate the spread of the infectious disease, but state health officials warned that Thursday’s one-day high of 1,158 confirmed cases was an anomaly due to delays by one lab.

A glut of 19,000 test results from samples collected in the past two weeks was turned over by Valley Medical after the state contacted the Burnsville-based medical provider about irregular reporting. Among those, 4,658 diagnostic tests and 265 positive infections with the coronavirus that causes COVID-19 were included in Thursday’s daily report and padded the totals.

While an official for Valley Medical said all patients with positive tests were informed directly within 24 hours, the Minnesota Department of Health said this delayed notification to the state hurts its ability to combat the broader pandemic.

“Delayed reporting ... means that 265 people who tested positive for COVID-19 were not contacted by health officials in a timely manner,” the department said in a statement. “This creates multiple problems — not only does it mean the person tested is unaware of their infection and the need to self-isolate to protect family, friends and close contacts, but it also delays our case investigation work and makes it harder to slow the spread of this disease.”

The confirmed infections bring the state’s total count in the pandemic to 72,390. The state also confirmed 13 deaths — the second straight day of double-digit totals — bringing that total to 1,806.

Thursday’s daily count was still nearly 900 even without the Valley Medical test results — a significant number amid a period of relative stability in the pandemic in Minnesota. The state has been averaging about 630 new infections confirmed per day over the past two weeks. Hospital numbers have leveled as well this month — with the state on Thursday reporting 305 COVID-19 hospitalizations and 139 people who needed intensive care due to breathing problems or other complications.

Forty-four lab-confirmed infections have now been traced to the Sturgis Motorcycle Rally in South Dakota, including one person needing hospital intensive care.

Health officials on Thursday also disclosed an outbreak of several cases tied to an Aug. 22 wedding in Ghent, Minn., that included a dance at KB’s Bar and Grill.

Anyone at the event in Lyon County in southwestern Minnesota who is concerned about exposure should seek testing, health officials said. Anyone at moderate risk must stay in quarantine for 14 days after they were potentially exposed to the virus, regardless of test results.

Health officials earlier noted a similar group outbreak in neighboring Lincoln County tied to a campground concert.

Funerals, tubing parties and graduation gatherings have all collectively contributed hundreds of infections, state health officials said. There have been 563 cases traced to large group events including 12 church outbreaks, 32 social gatherings, 14 weddings and two funerals.

The state has advised college students to “lay low” and avoid such large events in the two weeks before returning to campuses this fall to maximize the chances that they arrive virus-free. There have been 254 infections associated with colleges and universities, including 90 people — mostly students — who were infectious on campus. Fifty-one colleges have reported at least one case in the past two weeks and seven have reported five or more cases.

Health officials warned that COVID-19 numbers in upcoming days could be elevated as they process the test results sent from Valley Medical.

Valley Medical used its lab for toxicology screens for pain management and addiction patients before converting in May to support the state’s crush of COVID-19 testing needs.

With drive-through sites in Burnsville, Minneapolis and Woodbury, the provider is collecting around 500 samples for COVID-19 testing each day, said Jerald Mackey, Valley Medical’s manager of operations.

Mackey said it’s frustrating that his relatively new lab was called out by name, but he understood why the Health Department wanted to explain the reasons for Thursday’s increase in confirmed cases. Changes in processes will prevent future backlogs, he added.

“It’s not the favorite way I guess to have your name put out there, but I also think it’s important that transparency exists,” he said. “We understand the rule and are following it.”

Minnesota generally requires the confirmation through testing of infectious diseases such as hepatitis or meningitis to be reported to the state in one working day. That requirement was extended in March to COVID-19 cases.