GREENWICH — The work of contact tracing began Wednesday to determine who may have come in contact with a Greenwich High School teacher who tested positive for COVID-19, the school district confirmed.

The teacher had been self-quarantining since Friday night and has not been inside the school building this week, according to a letter sent to families and students Tuesday night from Superintendent of Schools Toni Jones and the district’s Head of Nursing Mary Keller.

Greenwich Public Schools Director of Communications Sasha Houlihan said Wednesday night that classes would proceed as scheduled Thursday at Greenwich High.

“Contract tracing was initiated and the minimal number of students and staff impacted were personally notified to quarantine,” Houlihan said.

The district said it learned Tuesday night that the teacher had tested positive. In partnership with the town Health Department, it will begin contacting students Wednesday who may have come in contact with the teacher before they return to the school Thursday.

Wednesday is a remote learning day for all Greenwich High School students.

“Although the necessary safety protocols are in place in our schools, including masks, social distancing and enhanced cleaning procedures, we may see limited incidences similar to other districts in Fairfield County and around the state,” Board of Education Chair Peter Bernstein said Wednesday afternoon. “We will continue to be vigilant regarding the health and safety of our students and staff and rely on the Greenwich Heath Department and Connecticut Department of Public Heath in terms of forward guidance.”

Additional testing of staff will also continue to take place, Jones said in the letter.

“In an effort to be proactive, GPS began optional COVID-19 testing for staff last week,” the letter said. “GPS tested approximately 50 GHS staff members last Friday and all results were negative. GPS will remain vigilant in keeping our families informed as guided by our local health officials.”

In addition, a Greenwich High School student was sent home Tuesday after learning a family member had tested positive for COVID, the district said. The family member had been in quarantine a week before learning the results, and the student had no contact with the family member in that time period, according to the district.

“Out of an abundance of caution, the student will quarantine for 14 days at home and will be tested,” Jones’ letter said. “The student has not experienced any COVID-19 symptoms.”

According to the district, they will keep families and students informed if the student tests positive.

Before the start of school, the district confirmed that three staff members had tested positive for the coronavirus and that a fourth was in quarantine as a result of possible exposure. None of the staff members had been in school buildings at that point, according to the district. Greenwich Public Schools did not provide information as to where in the district the staff members were employed.

Middle school students at Greenwich Catholic School were sent into remote learning until Sept. 26 after a seventh-grader at the school tested positive for the virus, school officials there said. Schools throughout the state, including in Stamford, New Milford and Westport, have also been forced to close temporarily in the days and weeks since reopening because of coronavirus cases.

First Selectman Fred Camillo said he had been in touch with the school district and the Health Department but didn’t have details on the scope of the contact tracing effort.

While Camillo said the case of COVID-19 was concerning, he cited the town’s ability to thwart other recent spikes by adhering to safety guidelines as reason for cautious optimism.

“Since day one, you always have to have a healthy bit of concern,” Camillo said. “But we have all the protocols in place and for the most part we’re seeing really good compliance on the part of our residents. But we knew there were going to be cases coming up.”

justin.papp@scni.com; @justinjpapp1; 203-842-2586