CHICAGO (AP) — Election officials are notifying hundreds of Chicago voters who went to the polls in last month’s primary of possible exposure to COVID-19.

The Chicago Board of Election Commissioners is sending letters to voters who went to at least four voting sites, including a site where a poll worker felt symptoms days later and died from the virus.

Spokesman Jim Allen says either poll workers or voters who had tested positive were at the sites on the March 17 primary and notified election officials. Illinois was among the first states to grapple with the idea of rescheduling its primary during the pandemic.