Chicago, Sep 21 : Chicago Public Schools (CPS), the third largest school district in the US, has reported 481 Covid-19 cases with more than 9,600 close contacts of an infected person identified in the first three weeks of in-person classes. The data on the district's public case tracker reflects 329 student cases and 152 adult cases for the period from August 29 through September 19, Xinhua news agency quoted the Chicago Tribune as saying in a report on Monday. The district's latest update shows more than 4,000 Covid-19 tests have been administered this school year through its screening program, with four people testing positive last week. The school district's voluntary testing program is not expected to expand to all schools until the end of the month. The testing program is only mandatory for unvaccinated staff members and unvaccinated or half-vaccinated student-athletes during their sports seasons. CPS has changed the type of Covid-19 case information it reports on its website to include the number of cases at non-school-based CPS locations under the "administration" category in Sunday updates. The district's new Virtual Academy for "medically fragile" students is also appearing in the data set, with zero cases reported. Nevertheless, CPS' online case tracker only includes data from some 500 district-run schools and not charter or contract schools that are part of the CPS orbit, but are independently managed. /IANS