Health officials have confirmed 69 people became ill after swimming in Lake Nokomis in Minneapolis, a week after the lake’s beaches were closed following an E. coli outbreak.

The update Tuesday from the Minnesota Department of Health means an additional 20 people have shown symptoms of bacterial infection since Friday. To contain the outbreak, the lake’s two beaches will remain closed for the rest of the season.

Of the 69 cases, 20% were children 10 years old or younger, according to Doug Schultz, a spokesman with the Department of Health. None of the sickened people have been hospitalized, he said.

Meanwhile, four other public beaches in Minneapolis remain closed for another week after showing levels of E. coli that exceeded state standards, according to the Minneapolis Park and Recreation Board. The season has brought the most beach closures at any one time since the city began testing for the bacteria in 2003.

The Park Board tested for bacteria in every lake but Nokomis on Monday. Theodore Wirth Lake Beach, Lake Hiawatha Beach and the beaches at Bde Maka Ska Thomas and Bde Maka Ska 32nd Street will stay closed for another week, said Park Board spokeswoman Robin Smothers.

For the Park Board to close a beach, the E. coli levels must exceed either the single-day or 30-day guidelines set by the Minnesota Pollution Control Agency.

That means a beach has either a single result of more than 1,260 E. coli bacteria organisms per 100 milliliters of water, or five samples over 30 days that exceed 126 organisms per 100 milliliters of water. All four beaches except for Nokomis were closed because they exceeded the 30-day guideline, according to the Park Board.

The beach at Theodore Wirth Lake, in west Minneapolis, has had an early closure in four of the last seven years, Smothers said. The Park Board, she said, believes the high E. coli levels are related to geese and other waterfowl that flock there during migration and befoul the beach.

The 69 people who became sick at Lake Nokomis swam at the lake between mid-July and mid-August, according to the Department of Health. Though some had a low-grade fever and vomiting, the majority suffered stomach cramps and diarrhea.

Neither the Park Board nor the Department of Health are testing Lake Nokomis since it will be closed for the remainder of the season.

“We may be able to find patient zero. ... However it’s not really that necessary,” Schultz said Tuesday. “It’s not something that we need to do in order to control the outbreak.”

Schultz said the Department of Health is urging people who are sick to stay out of the lakes, and for people who swim to refrain from swallowing the water.

The Park Board also recommends staying out of the water after it rains, when bacteria levels usually rise.

Park rules prohibit dogs and other pets from going in “park waters.”

The last bacteria test of the season is Monday. If the four beaches that are currently closed have low E. coli levels next week, they will reopen, Smothers said.

The swimming season ends Sept. 2, at which date beaches remain open but without a lifeguard on duty.