Montrose Beach. (Credit: Lisa Fielding)

Montrose Beach. (Credit: Lisa Fielding)

Updated 9/2/2013 at 5 p.m.

CHICAGO (CBS) –Officials imposed a swim ban at North Avenue Beach Monday afternoon, blaming hazardous surf. Meanwhile, nearly half of Chicago’s public beaches remained under swim advisories.

The decision about North Avenue came shortly after 3 p.m., as hundreds of people were trying to enjoy the popular beach on Labor Day. Lifeguards got to work, getting frolicking folks out of the water and hoisting the red warning flag, CBS 2’s Dana Kozlov reports.

Earlier, some swimmers told her they could feel a pull in the water.

Conditions weren’t expected to change anytime soon. The National Weather Service is expecting “life-threatening” rip currents along the shores of Lake Michigan until Tuesday evening.

“Dangerous pounding waves and life-threatening rip currents are expected at many of the Illinois and Indiana beaches,” the weather service said.

At Montrose Beach, many lugged their coolers, their beach blankets, volleyballs and grills to enjoy the last day off before work and for some, a new school year.

“Enjoying the beach. The end of summer. The water is a bit rough, nice big waves, nice big rollers. My wife and my son are bouncing around in the waves but they are strong swimmers. We’ll keep an eye out,” said Jim Boyle of Chicago.

“We were supposed to go sailing this morning but we couldn’t because there’s a small craft advisory so we rode our bikes to the beach. Not too deep, we’re just wading,” said Suzi Casparic, also of Chicago.

Montrose Beach. (Credit Lisa Fielding)

Montrose Beach. (Credit Lisa Fielding)

Rough waves could be seen and heard from several feet away from the shore. There are 21 lifeguards on duty at Montrose, three boats and several sand guards. Guards say they are keeping a close eye on swimmers and are corralling anyone closer who is too deep where the water is above their chest.

For the latest on beach advisories and swim bans at Chicago beaches, click here.

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