(CNN) More neighborhoods in Jackson, Mississippi were starting to flood Saturday as the swollen Pearl River may soon reach its highest point in decades, city officials said.

Authorities urged people in mandatory evacuation zones in Mississippi's capital to leave their homes or ask for help evacuating.

"Please, please get out before dark tonight," Gov. Tate Reeves said at a news conference, addressing hundreds of people whom officials have asked to evacuate near the river in the Jackson area.

As of Saturday night, the Pearl River, already moderately flooding some neighborhoods around northeast Jackson, had risen to nearly 36 feet and nearly 8 feet above flood stage, the National Weather Service said.

The river is expected to crest at 38 feet early Sunday, city officials said.

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