Milwaukee health officials said they had identified at least seven people who contracted the coronavirus from participating in Election Day on April 7, which was held despite a stay-at-home order issued throughout the state.

The seven people were the first identified by Milwaukee officials, who contend that the number may be higher as they are still conducting testing. Other cities have not reported any cases tied to voting yet.

The officials, in a statement issued Tuesday, did not say how they traced the new coronavirus cases to in-person voting. Six of the cases they identified were Milwaukee voters; the seventh was a poll worker.

Polling places opened across Wisconsin after the state’s Republican-controlled Legislature refused to take action to postpone the election or expand vote by mail. The Wisconsin Department of Health Services said it would also be studying any voters or election workers who contracted the virus from voting. They have not reported any cases yet.