NEW YORK — Oil prices closed below $100 a barrel for the first time in six months Monday, tumbling in another dramatic sell-off as the demise of Lehman Brothers and the sale of Merrill Lynch deepened worries about the U.S. economy.

Crude prices shed more than $5 a barrel and have now given up virtually all their gains for the year, extending a steep, two-month slide from record levels above $147 a barrel.

Oil's pullback also came as early signs suggested that Hurricane Ike delivered less damage than feared to the Gulf Coast energy oil and gas infrastructure. But pump prices jumped above $4 a gallon in parts of the country as a precautionary shutdown of Gulf refineries caused gasoline shortages.

The latest sell-off in oil began Sunday and accelerated Monday as traders digested a day of dramatic upheaval on Wall Street: Lehman Brothers Holdings, a 158-year-old investment bank, filed for bankruptcy after failing to find a buyer, and Merrill Lynch & Co. agreed to be bought out by Bank of America.

Lehman, Merrill and other big institutional investors were major participants in the commodities boom of the past year, helping push the price of oil, precious metals and grains to historic highs until a slowing global economy helped bring a halt to the rally.

Analysts said investors feared the upheaval in the financial sector could trigger another round of commodities liquidation — especially with Lehman likely to unwind its holdings.

PHILADELPHIA — Rising gasoline prices have trains so crowded that Philadelphia's regional rail conductors sometimes can't collect all the tickets.Many commuters now want to drive only to the nearest train station. That means parked cars are filling the lots at Southeastern Pennsylvania Transportation Authority stations and overflowing along nearby road shoulders.SEPTA rail operations have the highest ridership in 25 years, up 12 percent from a year ago. Crowds of passengers are standing on many rush-hour trains.The line is buying used rail cars, taking cars out of mothballs and making schedule changes to try to adapt. SEPTA also has 120 new rail cars on order. They are expected to start arriving in late 2009.

HARRISBURG — Foreclosure filings in Pennsylvania jumped 60 percent over last August, as adjustable-rate mortgage payments rise and the job market stagnates.RealtyTrac said 4,921 Pennsylvania properties received foreclosure filings last month, or about one in every 1,100 households.That amounts to an 18 percent increase from July, and it is 58 percent above August of last year. Both outpaced the national rate.However, Pennsylvania remains well below the national foreclosure rate, which was one in every 416 households in August.