Four more cases of a parasite that causes diarrhea have been found in Lawrence, a local health official announced Thursday.

They bring the number of cryptosporidium cases here from 11 to 15, Kay Kent, the Lawrence-Douglas County Health Department director, told the news media Thursday afternoon at her office.

Thirteen of those cases are associated with the Lawrence pools, she said. Four pools were closed Friday and Saturday to deal with the problem.

To help track any more cases, the Health Department is sending out surveys to parents of students at four Lawrence schools picked at random: Hillcrest, Prairie Park, Quail Run and Sunflower, Kent said.

The Health Department also will try to track other cases by conducting random phone surveys throughout the next several weeks, she said.

Kent said efforts to locate the source of the outbreak are being conducted by four officials from the federal Centers for Disease Control and one official from the Kansas Department of Health and Environment.

For more on this story, see the 6News report at 6 p.m. and 10 p.m. on Sunflower Broadband, channel 6 and pick up a copy of Friday’s Journal-World.