FORT LAUDERDALE, Fla. -- Health officials warned of extensive bacteria outbreaks at five South Florida beaches popular with spring break crowds.

The bacteria can increase the risk to swimmers of developing gastrointestinal diseases, such as hepatitis A, shigellosis and cholera, which can cause severe diarrhea and intestinal pain.

High levels of enterococci bacteria were detected Thursday in the water off two Fort Lauderdale beaches, Lauderdale-by-the-Sea, Pompano Beach and Gulf Stream.

Health officials also found high levels of fecal coliform bacteria off Hollywood and Hallandale Beach. Additional tests were planned Friday to determine whether warnings should be issued for those beaches as well.

Both types of bacteria are found in human and animal waste, but the state Health Department does not know what caused the outbreak. One possible source is sewage from a passing ship, said Tim O'Connor, of the Palm Beach County Health Department.

The state Health Department regularly tests water quality at popular beaches and issues warnings for a high bacteria levels a few times a year, but usually for smaller areas.

"I don't think we've ever had this many sites," said Howard Rosen, environmental administrator for the Broward County Health Department.

Health advisories were also posted for nine miles of beach in Volusia County, about 200 miles north of Fort Lauderdale. Health officials said they didn't know if the outbreaks were related.