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In a video news conference, Mayor Ras Baraka said the unidentified woman arrived at the hospital on Saturday, underwent the test, and provided a false name and address before leaving.
When city health officials arrived at the residence to notify her, they realized she had lied about her identity.
After days of searching, Baraka announced on Facebook that the woman had been found.
"UPDATE: We have located the woman that was reported to have tested positive for Coronavirus," he wrote. "Thank you everyone for your vigilance. If you have any questions please tune into the Virtual Town Hall tonight at 7 pm."
The number of people with coronavirus in the state was 267 as of Wednesday afternoon, and three people have died.
After declaring a state of emergency, Gov. Phil Murphy ordered bars and restaurants to stop dine-in service as of 8 p.m. Monday, “until further notice.” Takeout and delivery would still be available.
Fox News' Danielle Wallace contributed to this report