Gulf Oil Leak Has Stopped as Cap Is Tested, BP Says

"I am very excited that there's no oil in the Gulf of Mexico," BP Senior Vice President Kent Wells said about the flow Thursday afternoon, adding that the test had just begun, "and I don't want to create a false sense of excitement."

Engineers sealed the well's final valves, causing oil to stop flowing at 2:25 p.m. local time, Wells said. The seal will be monitored every six hours to determine the pressure levels.

President Obama called the end of the flow of oil into the ocean a "positive sign," but also warned that further testing was required.

The new cap put into place late Monday is seen as the best hope of stopping the massive leak that has been spilling oil into the Gulf for nearly three months, causing an economic and environmental disaster.

BP will continue drilling two relief wells that the company hopes will permanently shut down the damaged well. The first one, nearly 18,000 feet below the water's surface, is expected to be completed in the next several weeks, BP said.