MINNEAPOLIS (AP) — Contaminated water led to a record number of beach closures in Minneapolis this summer, the city's park and recreation board said.

Half of the city's 12 beaches were not safe to swim in at various times during the summer — the most since Minneapolis started a water sampling program in 2003, said Deb Pilger, the director of environmental management for the Minneapolis Park and Recreation Board.

Heavy rainfall was part of the problem.

"When we have a rain event, it brings in a lot of storm water runoff and that runoff brings in a lot of debris and bacteria from streets, yards, yard waste," Pilger said.

But officials said goose droppings also contaminated the water at some beaches, as well as people with an illness that got in the water.

"It is all about poop," said Trisha Robinson, who oversees the waterborne diseases unit at the Minnesota Health Department. "That's how people come down with these illnesses. It's about somebody, usually a person that has an illness, and they get in the water and just the small amount of poop that they have on their butt washes off into the water and it makes everybody else sick."

Statewide beach closures are not tracked, but the health department gets involved when there's an outbreak of illnesses because of dirty water — and this summer there were two separate outbreaks.

One outbreak in Lake Minnetonka in July likely sickened about 200 people, the health department said. In August, Robinson said 70 people contracted e-coli after swimming in Lake Nokomis. No one needed to be hospitalized during either outbreak, health officials said.

"We certainly have had a busy summer," Robinson said.

As of Thursday, five beaches in Minneapolis were still closed because of contaminated water.

Health officials are urging the public to stay out of the water if they're sick and to wait a day to go in the beach after heavy rainfall.