KEY WEST, Fla. (Reuters)—Florida's tourism gained a respite on Wednesday when tar balls found on Keys beaches were shown not to come from the Gulf of Mexico oil leak, but officials said the $60 billion-a-year industry was already taking a beating from the unchecked month-old spill.

With energy giant BP P.L.C. still struggling to contain its gushing undersea well that has spewed a huge rust-colored slick into Gulf waters, oceanographers have forecast crude from it will be carried by currents southeast to the Florida Keys and possibly even farther afield, to Miami and Cuba.

The spill has already dumped oil debris ashore, especially in Louisiana but also on the coasts of Mississippi and Alabama, threatening fisheries and wildlife refuges. The Obama administration is grappling with a widening environmental and economic disaster for which it holds BP responsible.

Wildlife and environmental groups accused BP of holding back information on the real size and impact of the growing slick, and urged President Barack Obama to order a more direct federal government role in the spill response.

To the relief of Florida officials, the Coast Guard said laboratory tests had shown that 50 tar balls found this week on the Lower Keys—a mecca for divers, snorkelers, fishermen and beach goers—were not from the Gulf spill.

Local tourism authorities said damage had already been inflicted by the negative publicity linked to the spill.

"Even if we don't get even a gumball-sized tar ball down here in the next month, there has already been significant perception damage to Florida Keys and Florida tourism," said Andy Newman of the Monroe Tourism Development Council.

"We understand we are not out of the woods yet, that there's more oil out there," he said.

Mr. Newman said tar balls were not uncommon in the Florida Keys, as 8,000 commercial vessels pass through the Florida Straits each year and some, defying anti-pollution rules, wash fuel oil from their tanks, which then forms into balls.

But he hoped the news there was no link to the oil spill would be good for this month's Memorial Day weekend.

BP gave no update on its efforts to contain the spill.

It said on Tuesday a siphon tube was capturing an estimated 2,000 barrels (84,000 gallons) per day from the ruptured undersea Macondo well, about 40% of the amount that was gushing out.

BP shares closed down nearly 2% in London.

'Crime scene'

Environmentalists warn that the spill, which followed an April 20 explosion aboard the Deepwater Horizon drilling rig in the Gulf, could prove worse than the 1989 Exxon Valdez disaster off Alaska—the worst such incident in U.S. history.

In prepared testimony for a congressional committee, National Wildlife Federation President Larry Schweiger said BP had failed to disclose results from its tests of chemical dispersants used on the spill. He also said it had tried to withhold video showing the true magnitude of the leak.

"The federal government should immediately take over all environmental monitoring, testing and public safety protection from BP," Mr. Schweiger said. "The Gulf of Mexico is a crime scene and the perpetrator cannot be left in charge of assessing the damage."

The Washington-based Center for American Progress published comments by its health experts Lesley Russell and Ellen-Marie Whelan saying the huge spill, and the dispersants being used against it, posed "insidious and unknown" human risks.

Noting the federal government had allowed BP to test the undersea use of dispersants, they added: "But are we letting the fox guard the hen house by letting the oil companies determine the safety of these cleaning agents?"

In a sign of the widening environmental impact, the United States nearly doubled a no-fishing zone to 19% of U.S. waters in the Gulf seen affected by the spill.

The spill has forced Obama to put a hold on plans to expand offshore oil drilling and has raised concerns about planned oil operations in other areas like the Arctic.

London-based BP, which has seen its reputation battered and market value cut by $30 billion, has said it plans to increase the amount of oil it siphons as it works on a permanent fix.

But with most of the leaking oil still gushing unchecked, upbeat media pronouncements by BP CEO Tony Hayward, which have played down the size of the oil spill and its environmental impact, have angered U.S. Gulf Coast residents who fear their livelihoods will be destroyed.

Slick growing 'exponentially'

"I'm fielding lots of calls with questions about fishing in the Keys, especially from people that have reservations two or three weeks out...I have not lost business, yet, but expect I will when the spill, in whatever form, gets here," said Andy Griffiths, who owns a charter company in Key West.

Gulf Coast shrimp and oyster fishermen and boat operators say their business has already plummeted.

Of all the threatened states, Florida has the most to lose. Tourism is its economic lifeblood, its largest industry, generating $60 billion in spending from more than 80 million visitors a year, bringing in 21% of all state sales taxes and employing nearly 1 million Floridians.

Many forecasters see oil from the massive spill being sucked by a powerful ocean flow, the Loop Current, around the Florida Keys and possibly up to Miami beaches.

The National Oceanic and Atmospheric Administration said oil sheens have been seen on the current's northern edge. Private forecasters believe oil is already in the current.

The St. Petersburg Times quoted a Coast Guard official as telling members of Florida's congressional delegation that oil in the Loop Current would widen the prevalence of tar balls. "What has been a relatively confined expansive slick will now grow exponentially," said Rear Adm. Paul F. Zukunft.

Authorities have stressed the accident's so-far-limited impact on the region's fisheries, coastal shorelines and wildlife, but that has failed to allay residents' fears.

BP has said it will cover the costs of the spill. It estimated the bill for the oil cleanup at $625 million, with analysts saying costs could reach into the billions.

But President Obama's drive to lift corporate liability limits for oil spills stalled in the U.S. Senate on Tuesday.

BP, rig operator Transocean Ltd., and another contractor involved with the ruptured well, Halliburton Co., have traded blame about last month's accident.

The chief executive officer of Halliburton said on Wednesday that the company does not expect to incur costs related to its work on the blown Macondo well.