Maryland officials ordered a private lab that conducted the vast majority of coronavirus tests at clinics run by Montgomery County to cease testing Friday, after an inspection by state and federal officials found deficient practices.

The order from Maryland’s Office of Health Care Quality follows the county’s announcement a day earlier that it paused testing at two county-run sites pending a review of Rockville-based AdvaGenix’s testing process. An expanded closure Friday left Montgomery with no county-operated testing sites.

Following a complaint about the lab, inspectors found deficiencies that might have affected the integrity of samples and “call into question the reliability of the test results” for 17,254 people who were tested, according to a letter sent Friday from the state to AdvaGenix.

“These deficiencies pose an immediate jeopardy to the public health because the persons tested cannot rely on the questionable test results and may inadvertently and unintentionally contribute to the further spread of COVID-19,” the letter said.

It wasn’t known Friday whether tests conducted by the lab have shown incorrect results.

The lab has agreed to stop testing and notify the patients it had tested, according to a statement from the state health department. AdvaGenix officials did not respond to requests for comment Thursday or Friday.

Montgomery County Health Department spokeswoman Mary Anderson said AdvaGenix administered about 88 percent of the county’s tests. She said Montgomery typically has eight county-run clinics each week.

“Testing is canceled for all of our sites until further notice,” a notice on the county’s website said. “We will resume testing as soon as possible.”

Gov. Larry Hogan (R) has directed the state to supply the county with 5,000 test kits each week to make up for the shortage.

A clinic in Wheaton operated Friday with a limited supply of other tests, and then was set to close.

County officials announced Thursday that they closed two coronavirus testing sites, citing complications with the processing of tests by AdvaGenix, but they expanded that closure Friday to include other county-operated sites.

The first sites to close were at the Silver Spring Civic Building and White Oak Community Recreation Center, which collectively process about 1,100 tests each week. They were closed out of “an abundance of caution,” Montgomery health officer Travis Gayles said.

Gayles recommended that anyone tested at a county-sponsored clinic in the past two weeks get retested at a community-based clinic. The tests completed by AdvaGenix in the past two months represent about 8 percent of all tests in the county during that time, according to the county.

The other tests were conducted at clinics not operated by the county, which weren’t affected by the state’s order. The county’s contract with Adva­Genix provided for self-administered tests primarily for those who were asymptomatic.

Montgomery County’s seven-day average caseload stood at 97 infections Friday, a number that has changed little over the past two months. Maryland’s largest jurisdiction records an average of about one virus-related death each day.

Statewide numbers show Maryland is averaging its lowest number of daily infections in nearly a month, led by declines in the Baltimore region after earlier increases there. Maryland records about 10 virus-related deaths each day, a number that has held steady since early July.

Hogan urged residents to use caution during the weekend to avoid coronavirus transmissions.

“This weekend, protect your fellow Marylanders by avoiding crowds, washing your hands, and wearing a mask,” he tweeted.

D.C., Virginia and Maryland reported 2,025 new coronavirus cases and 18 additional fatalities Friday. D.C. reported 94 cases and no deaths, Virginia reported 1,216 cases and seven deaths, while Maryland reported 715 cases and 11 deaths.

Virginia’s number of daily infections was the highest since Aug. 8 and surpassed the state’s seven-day average caseload of 994.

Arlington County’s 42 new cases Friday was its largest daily increase since May 29. The county’s seven-day average of 20 new daily cases has nearly doubled since late July.

Each Northern Virginia jurisdiction Friday reported a daily increase higher than its seven-day average. The state’s Washington suburbs are hovering near 230 new daily cases after about six weeks of holding steady near 175 daily cases.

The virus’s death toll across the greater Washington region has fallen to levels that were recorded before a spike that began late last month. The seven-day average number of fatalities across D.C., Maryland and Virginia stood at 18 on Friday, down from 32 earlier in the month.