State health officials said anyone who was at the Portland International Jetport on Sunday could have been exposed to COVID-19 by two people, a person who is infected and a close contact, who boarded a flight to Florida and had to be removed.

In another development Monday, the outbreak at the Sanford school district grew to 12 people associated with the high school and regional technical center.

The individual who tested positive and a close contact went to the airport on Sunday afternoon despite being told to isolate, the Maine Center for Disease Control and Prevention said in a written statement.

“The individual with COVID-19 tested positive late last week and was directed to isolate,” Robert Long, Maine CDC spokesman, said in the statement. “This individual’s close contacts were also directed to quarantine.

“Maine CDC staff became aware Sunday that the individual and one close contact intended to fly to Florida. Maine CDC staff communicated with the individual with COVID-19, who subsequently chose not to board the aircraft. The close contact of that individual was removed from a plane before takeoff and has not been confirmed to have COVID-19.”

The agency is advising anyone who was at the airport between 12:30-4 p.m. on Sunday to monitor themselves for symptoms and consult with a health care provider to determine whether they should be tested.

Paul Bradbury, Portland International Jetport director, said that the airline removed the passenger, and that Portland police officers assigned to the jetport were not involved. Any legal sanctions, such as citations for failure to follow Gov. Janet Mills’ executive orders designed to limit the spread of COVID-19, would come from the Maine CDC, Bradbury said.

“I’m not sure there was any ill will on anyone’s part,” Bradbury said. “There was poor judgment.”

Long did not respond to questions on Monday afternoon from the Press Herald about whether the person with COVID-19 or the close contact who boarded the airplane would be cited by the Maine CDC.

The person with COVID-19 returned to isolation, and the close contact went into quarantine, the Maine CDC said.

“People with COVID-19 must isolate until a public health official can confirm that they meet the criteria for recovery,” Long said. “Close contacts of people with COVID-19 must quarantine for 14 days, regardless of whether they receive a negative test result.”

The Maine CDC is advising anyone who was at the Portland International Jetport between 12:30 and 4 p.m. on Sunday to monitor themselves for coronavirus symptoms and consult with a health care provider to determine whether they should be tested. Derek Davis/Staff Photographer Buy this Photo

Bradbury said that he does not know how many airport employees would need to be tested, if the exposure was considered to have been long enough to warrant COVID-19 testing. Airport employees are required to wear masks and other personal protective equipment. Visitors to the airport are required to wear masks.

“The Maine CDC really worked quite quickly to respond to this situation and remove the individual from the plane. The system worked to limit exposure,” Bradbury said.

Also on Monday, the Maine CDC reported another death and 29 new cases of COVID-19, including 18 in York County, which remains a hotspot for new infections.

Matt Nelson, superintendent of the Sanford School Department, posted a letter on the district’s website Monday advising the community that 12 people associated with Sanford High School and the Sanford Regional Technical Center had tested positive. Four tested positive before the start of school and had not been at the schools.

The letter said the district was consulting with the Maine CDC and Department of Education to identify and notify anyone known to have been in close contact with one of the eight individuals who tested positive since returning to school.

“Please understand there is a possibility that other staff or students may have encountered individuals who tested positive and had exposure to the virus,” Nelson said. “A Maine CDC or school representative will contact you directly if you are identified as a close contact of someone who has tested positive.”

The seven-day daily average of new cases of 30.4 has doubled when compared to mid-August, when the seven-day average was about 15. The average has remained at about 30 over the past week.

Since the pandemic began, 5,106 people have contracted COVID-19, and 140 have died.

Much of the growth in cases in York County has been linked to a crowded wedding and reception in the Millinocket area, where attendees were not wearing masks or practicing social distancing. The Aug. 7 event has directly or indirectly led to at least 177 cases and eight deaths, including seven at a nursing home in Madison.

York County outbreaks have been recorded at the county jail, Calvary Baptist Church, five social clubs in the Sanford area, Sanford High School and the Portsmouth Naval Shipyard in Kittery.

Sanford High School moved to all-remote learning on Monday in response to the outbreak, and York County schools have been designated “yellow” under the state’s color-coded advisory system for school reopening. All fall sports in York County have been put on hold as a result of the outbreaks and spiking case numbers.

Since late August, Maine officials have stepped up enforcement for pandemic-related business regulations, issuing citations to 14 establishments for “imminent health hazards” related to virus control.

Also, Falmouth High School reported its first case of COVID-19, but the school’s hybrid plan will continue based on advice from the Maine CDC, according to a letter Superintendent Geoff Bruno posted on the Falmouth schools website.

“The person presented symptoms late Thursday night and did not attend school on Friday,” Bruno’s letter said. “The person has not entered the school campus since Tuesday (Sept. 15), more than 48 hours prior to becoming symptomatic.

Typically, the infectious period (symptomatic cases) is two days before symptom onset, per CDC. We are pleased that our screening system was effective: the person was contacted, kept out of school, and tested for COVID 19.”