BP's much-anticipated attempt to cap its undersea gusher in the Gulf of Mexico, a spill now estimated at twice the size of the Exxon Valdez disaster, was suspended for more than 16 hours before it was restarted late Thursday afternoon, a BP executive said Thursday.
"This whole operation is very, very dynamic," Doug Suttles, the company's chief operating officer.
"When we did the initial pumping (Wednesday), we clearly impacted the flow of the well. We then stopped to monitor the well. Based on that, we restarted again. We didn't think we were making enough progress after we restarted, so we stopped again."
The light-brown material that was seen spilling out of the well throughout Thursday was the previously pumped fluid from the "top kill" procedure mixed with oil, he said.

"I probably should apologize to folks that we haven't been giving more data on that," Suttles said when asked why it took so long for BP to announce it had suspended the top kill. "It was nothing more than we are so focused on the operation itself."

Suttles said part of the problem is that too much mud is leaving the breach instead of going down the well. "So what we need to do is adjust how we are doing the job so that we get more of the drilling mud to go down the well," Suttles said.
He said one solution would be to introduce solids -- known as "bridging material," or its variant "junk shot" -- into the mix.

BP officials say the procedure could take another 24 to 48 hours to complete, though whether the top kill will successfully stop the flow of oil is uncertain.
Enormous brown plumes of drilling "mud" billowed from the damaged well during the process, which BP Managing Director Bob Dudley called "a "titanic arm-wrestling match" a mile below the surface.
Coast Guard Adm. Thad Allen, who is leading the government's response to the oil spill, earlier said the work "is moving along as everyone had hoped."
"They're pumping mud into the well bore, and as long as mud is going down, hydrocarbons are not going up," Allen told reporters Thursday afternoon. The work could take another night, he told reporters in Venice, near the mouth of the Mississippi River.
"I think we just need to let that run its course, and we will see what happens," Allen said. However, asked about reports the procedure had been halted, Allen said he hadn't talked to BP officials yet.
Stopping the leak took on even more urgency after government scientists released spill estimates that far exceed the previous 5,000-barrel-a-day number given by BP.
The burst well is spewing oil at a rate of at least 12,000 to 19,000 barrels a day, U.S. Geological Survey Director Marcia McNutt told reporters Thursday, meaning 260,000 to 540,000 barrels had leaked as of 10 days ago -- larger by far than the 250,000 barrels spilled when the tanker Exxon Valdez ran aground in Alaska's Prince William Sound in 1989.
The 38-day-old spill was beginning to take its toll on Louisiana's sensitive coastal marshes, where heavy oil has been killing plant life and fouling local wildlife and fisheries. On Thursday, the eve of the Memorial Day holiday weekend, the beaches of Grand Isle were empty.

"If only it gets stopped, if what they did yesterday works, that's the beginning of the end," Grand Isle Tourism Commissioner Josie Cheramie said. "We can clean up what's already been put out there, but we just really need to get it stopped. That's the main thing."
The spill claimed a job in Washington, as the head of the scandal-plagued federal agency that oversees offshore drilling resigned.