TEXAS CITY, Texas - Tar balls found over the weekend on a Texas beach were confirmed Monday as the first evidence that crude gushing from BP's ruptured Gulf of Mexico oil well has reached all the gulf states.

A Coast Guard official said it was possible the oil hitched a ride on a ship and was not carried naturally by currents to the barrier islands of the Texas coast, but there was no way to know for sure.

The amount was tiny in comparison with what has coated beaches in the hardest-hit parts of the Gulf Coast in Louisiana, Mississippi, Alabama, and the Florida Panhandle. Still, it provoked the quick dispatch of cleaning crews and a vow that BP will have to pay for the trouble.

"Any Texas shores impacted by the Deepwater spill will be cleaned up quickly and BP will be picking up the tab," Texas Land Commissioner Jerry Patterson said in a news release.

Earlier Monday, BP P.L.C. said the costs of tackling the leak, in its 76th day, had risen nearly half a billion dollars in the last week, to $3.12 billion, including for work on cleaning and capping the gusher and payouts to individuals, businesses, and governments.

London-based BP, the largest oil and gas producer in the gulf, said the total cost rose from $2.65 billion a week earlier. The figure is separate from a $20 billion fund for damages that BP created last month under pressure from the White House.

The company is also billing its partners in its Deepwater Horizon venture, Anadarko Petroleum Corp. and Japan's Mitsui, for their shares of the cleanup.

BP has billed Anadarko, a 25 percent stakeholder in the blown-out well, for more than a quarter-billion dollars. It has reportedly billed Mitsui, a 10 percent partner, $111 million.

The oil's arrival in Texas had been predicted Friday by an analysis from the National Oceanic and Atmospheric Administration, which gave a 40 percent chance of crude reaching the area.

"It was just a matter of time that some of the oil would find its way to Texas," said Hans Graber, a marine physicist.

About five gallons of tar balls were found Saturday on the Bolivar Peninsula, northeast of Galveston, said Capt. Marcus Woodring, the Coast Guard commander for the Houston/Galveston sector. Two gallons were found Sunday on the peninsula and Galveston Island, though tests have not yet confirmed its origin.

Woodring said the consistency of the tar balls suggested that they could have been spread to Texas water by ships working out in the spill. But there was no way to confirm how they got ashore.

The largest tar balls, found Saturday, were the size of table-tennis balls, while the ones found Sunday were the size of nickels and dimes.

Galveston Mayor Joe Jaworski said he believed the tar balls were a fluke, rather than a sign of what's to come.

"The water looks good," he said.

The distance between the western reach of the tar balls in Texas and the most eastern reports of oil in Florida is about 550 miles. Oil was first spotted on land near the mouth of the Mississippi River on April 29.

The spill is reaching deeper into Louisiana. Strings of oil were seen Monday in the Rigolets, one of two waterways that connect the gulf with Lake Pontchartrain, the large lake north of New Orleans.

"So far it's scattered stuff showing up, mostly tar balls," said Randy Pausina, the Louisiana Office of Fisheries' assistant secretary. "It will pull out with the tide, and then show back up."

Pausina said he expected the oil to clear the passes and move into the lake, taking a backdoor route to New Orleans.

The news of the spill's reach came as most offshore skimming operations in the gulf were halted by choppy seas and high winds. A tropical system that had been lingering off Louisiana flared Monday afternoon, bringing heavy rain and winds.

Last week, the faraway Hurricane Alex idled the skimming fleet off Alabama, Florida, and Mississippi with choppy seas and stiff winds. Now the fleet is stymied by a succession of smaller storms that could last well into this week.

Skimming operations have scooped up 23.5 million gallons of oil-fouled water so far.

The storms have not affected drilling work on relief wells that BP says are the best chance for plugging the leak. The company expects drilling on one well to be finished by mid-August.

High seas over the weekend also hampered the test run of the so-called super-skimmer, a retrofitted 1,100-foot tanker called the A Whale. Bob Grantham, a spokesman for boat owner TMT Shipping Offshore, said Monday that the weekend tests were "inconclusive" because of rough seas, the Los Angeles Times reported.

The ship takes in an oil-water mixture through slits and then sends it through a series of tanks to separate the oil from the water.

The super-skimmer is among a number of novel tools being thrown into the ever-growing containment and cleanup effort, which now engages 44,500 workers.

BP also has bought centrifuges from actor Kevin Costner, and it has shipyards cranking out the Heavy Oil Recovery Device - both designed to collect oil too heavy for skimmers.

A Navy blimp, the MZ-3A Airship, is on its way to the gulf from Yuma, Ariz. The 178-foot-long airship will stay close to shore, helping skimmers find patches of oil and keeping an eye out for marine mammals and other wildlife.