ST. PETERSBURG — Pinellas County environmental officials have reported hundreds of thousands of dead fish on and off the coast of area beaches stretching more than 20 miles from Clearwater to St. Petersburg, confirming that Red Tide has reached the Tampa Bay area.

The first report of fish kills came from the city of Clearwater on Friday, said Kelli Levy, Pinellas' director of environmental management. Around noon Saturday, the city of St. Petersburg reported "hundreds of thousands" more.

PREVIOUS COVERAGE: Red Tide's toxic toll — your questions answered (w/video).

Madeira Beach, Redington Beach and Treasure Island have also been affected, she said. Levy could not provide an overall estimate of how many fish have been found.

Many that floated ashore have been cleaned up by crews from the county and the involved cities that worked throughout the day Saturday. Still, Levy said she expects the clean-up to run through the weekend and into next week, as many dead fish are still floating offshore.

As of Saturday evening, a boat was circling the Intercoastal near Clearwater Pass, scooping hundreds of dead fish off the water's surface to prevent them from reaching the beach, Levy said. More boats provided through a contractor hired by the county will arrive Sunday morning to help.

The collected fish are put into dumpsters stationed at each beach, and will be taken to the county's landfill for burial, Levy said.

"It's a huge community effort of all of us working together," Levy said. "We did a lot today getting logistics in place, tomorrow we'll have a lot more done, and on Monday and Tuesday, we will be in full operational mode."

RELATED: Why is Red Tide so bad this year? Could dust from the Sahara be to blame?

RELATED: Clues to combating Red Tide are found in mounting manatee carcasses

Small, scattered colonies of microscopic algae live in the Gulf of Mexico all year long. Usually, their numbers are so low they are undetected. But sometimes in the late summer or fall, the algae population 10 to 40 miles off shore explodes into what's called a bloom. The algae multiply so quickly, covering the water's surface and staining it with a rusty color — giving the phenomenon its name. Winds and currents push it ashore.

The toxic algae kills fish, as well as sea turtles and manatees. It can have mild affects on humans, too. While it's usually limited to slight irritation and coughing, it can pose risks for those with asthma and other respiratory problems.

The Red Tide has lingered just south of Pinellas, near the Sarasota area, for weeks.

But by Saturday afternoon, it had reached waters off Pinellas.

RELATED: Recalling the devastating Red Tide of 2005 and dreading a repeat

Andres and Veronica Bernal were lounging on St. Pete Beach late Satuday afternoon when their six-year-old son started screaming.

"He was completely upset and having a total melt down," Andres said.

The sudden emergence of Red Tide surprised the Bernals. Veronica had checked all of the county websites before leaving Tampa around 2 p.m. to see what beach they should go to. Everything said St. Pete Beach was clear so they piled into the car and made the trek.

"I did my research, searched to see if anybody was talking about red tide being at the beach and found nothing," Veronica said. "So we came."

They salvaged their beach outing by limiting their son and four-year-old daughter to play in the sand. The kids were too scared to go in the water with the dead fish around them — and the parents were concerned.

By Saturday evening, the stench of decomposing fish hung in the air.

As the tide went out throughout the day, fish slowly started to come ashore, one after another.

Seagulls lurked by the masses, devouring the carcasses one by one.

Adam Chilbers is visiting from Indianapolis with his friend Justin Borneman who lives in St. Pete. He was disappointed to see the Red Tide — more because he knows the effects it has on the environment — than for swimming.

"It didn't bother us," Chilbers said. "We dove right in."

Things at Clearwater Beach Saturday night seemed fairly normal, busy with beachgoers and tourists. Levy said most of the dead fish found there had been cleaned up by that time.

At Madeira Beach, however, dead fish dotted the shoreline. Marin Klapuh, 17, came from Seminole to see the sunset with friends and was stunned to see how many there were.

"I had heard about it, but I didn't know it was going to be this bad," he said. "It's kind of tragic, to be honest, to see the fish like this."

Contact McKenna Oxenden at moxenden@tampabay.com. Follow @mack_oxenden. Contact Megan Reeves at mreeves@tampabay.com. Follow @mareeves