OCEAN RIDGE, Fla. — Along with a warning about rough surf at Deerfield Beach about an hour north of Miami was this: "Possible red tide."

"My throat tickled so bad," said Weslynn Davis, who was coughing at the beach.

The problem is caused by toxic algae and prolonged exposure can lead to more serious health issues. The algae is naturally-occurring, but massive blooms along Florida's West Coast, believed to be fueled by pollution, have killed fish and other marine life.

Now, dead fish have started to pop up on Florida's East Coast where red tide is rare. Scientists are looking into whether currents carried the algae over, or whether it sprung up on its own.

It's been detected in Palm Beach and Miami-Dade counties, where certain beaches have closed. Testing continues in the greater Miami-Fort Lauderdale area, which depends on its beaches for millions in tourist dollars.

"Nutrient pollution, things like agricultural runoff and fertilizer runoff from peoples' lawns, discharge from septic systems and wastewater treatment plants, those are all things that can exacerbate the problem," said Dr. Malcolm McFarland, with Florida Atlantic University.

Runoff from Lake Okeechobee, for example, is loaded with pollutants from industrial agriculture and development. Dr. McFarland said it remains to be seen whether this will be an ongoing problem.

There's no telling how long the red tide will last or it's possible economic impact on Florida's East Coast, especially as the tourist high season kicks in. But on Thursday, Gov. Rick Scott pledged $3 million for counties impacted.