Thursday's USA Today:

Analysts said liquidity problems at oil and asphalt transportation and storage provider SemGroup LP may have helped trigger the recent sell-off. A number of the company's subsidiaries filed for reorganization under Chapter 11 bankruptcy rules in Delaware federal court Tuesday.

In the bankruptcy filing, the Tulsa-based company described what it called a "severe liquidity crisis" caused by demands for massive amounts of more money from brokers to cover large bets it had amassed on futures and options. Those demands grew increasingly tough to meet as energy prices rose and Wall Street's credit problems mounted.

On July 16, a day after oil prices began to tumble, the company transferred its trading account and in the process recognized $2.4 billion in losses as it became clear it could not cover its trading positions. Co-founder and former President and CEO Thomas Kivisto owes about $290 million of that total.

"It turns out that the run-up in crude oil prices in June and early July had ... a lot to do with the squeeze on SemGroup's hedges," analyst and trader Stephen Schork said. "Now the only question is are there more 'SemGroups' lurking in the shadows?"