FOLLY BEACH -- Casey Bowers got a whiff of the strong odor here and figured someone had tossed dead fish into a trash can near the Holiday Inn.
Then Bowers saw the heavy equipment plowing the beach southwest of the fishing pier and wondered if oil from the Gulf spill was washing up.
"It scared me," the Folly resident said.
What actually occurred was just as unusual, a massive wave of Mulinia shells has blanketed part of the beach for a week.
Many of these fingernail-size clams died and have caused such a stink that city officials figured they had to do something.
On Wednesday, more than a dozen workers with G&C Utilities Inc. began scooping up millions of the shells and burying them in trenches about three feet deep.
Darren Melton, 21, has lived on Folly all his life but has never seen anything like this.
"I noticed the smell last week," he said. "I figured something washed up and died."
Amber Henline of Spruce Pine, N.C., said she took a walk on the beach Tuesday night and couldn't avoid the huge carpet of shells.
"It was overwhelming. It reeked," she said. "It's kind of like rotting fish."
On Wednesday afternoon, a strong ocean breeze kept the water's edge smelling fine, but the pungent smell was noticeable from Center Street and other inland spots.
State officials aren't sure what caused the die-off, said Phil Maier, coastal reserves manager with the Department of Natural Resources.
"This is obviously an unusual event," he said. "At this point, there is no smoking gun."
Maier said biologists first thought the shells were Coquina shells, but they are Mulinia. While high temperatures and low oxygen levels originally were thought to be involved, Maier said if that were the cause, other sensitive species also would be affected.
He said the cause is more likely a disease or parasite, but biologists will know more later this week, after they process water samples and other tests.
"One other interesting piece is that a similar event occurred in 1993 in Georgia on St. Catherines Island," he said. "They never determined what caused it, and it has never reoccurred."
Folly Mayor Tim Goodwin said the city couldn't wait for the tides to remove the shells -- not after some people began complaining about the smell and checking out of local hotels early. And not with the busy Fourth of July weekend coming up.
"This is the first time anyone can remember this many showing up at any one point in time," Goodwin said. "It's kind of like any other natural disaster. You have to clean it up."
Bud Hinson, owner of G&C Utilities, said the challenge in clearing the beach was working around the tides.
As the tide receded Wednesday afternoon, more than a dozen workers were using rakes and heavy equipment to scoop up the shells and haul them away for burial.
He estimated they already had buried about 100 cubic yards of shells and sand so far that day.
Work will continue today, and Hinson said Folly's beachgoers have been good about going around the yellow caution tape and avoiding the workers.
"They understand," he said. "They want the aroma to go, too. They want the rest of their week to be nice."