Scientists said on Monday that BP's damaged Gulf of Mexico well gushed about 5 million barrels of oil after an April 20 explosion that killed 11 oil rig workers.

Scientists in the Flow Rate Technical Group said that the Macondo well sent 4.9 million barrels of oil, 205.8 million gallons, into the gulf before it was capped. The Washington Post has reported that the number far exceeds previous estimates and all but established the Deepwater Horizon disaster as the worst oil spill ever in the gulf.

It also ranks second on Wikipedia's list of largest known spills behind the Lakeview Gusher in California that spilled 378 million gallons between May 1910 and September 1911. The 1991 Gulf War spill in the Middle East leaked an estimated 84 million to 250 million gallons.

Working with the U. S. Geological Survey and the U. S. Department of Energy, the research group said the BP well initially gushed 62,000 barrels of oil daily. The scientists have said that the number fell to 53,000 barrels a day until the flow stopped July 15, when the damaged well was capped and sealed.

An attempt to begin plugging the well by pumping in mud and cement sustained a temporary setback Monday, the British company said on its Web site.

BP said in a statement, "During final preparations to commence with the injectivity test, a small hydraulic leak was discovered in the capping stack hydraulic control system. The injectivity test, previously announced to take place today, will be rescheduled until the leak is repaired. It is anticipated that the injectivity test and possibly the static kill will take place Tuesday."

It has also been reported that the operation was previously delayed for several days while crews cleared debris from Tropical Storm Bonnie.

CNN reported on Monday that BP Chief Operating Officer Doug Suttles said he had "a lot of confidence we'll be successful."

According to further reports, the static kill will be followed by a final "bottom kill" once a relief well intercepts the ruptured well. BP said that process could start five to seven days after the static kill is finished.

National incident commander Thad Allen, a retired U. S. Coast Guard admiral, said on Sunday, "We should not be writing any obituary for this event." (With Inputs from Agencies)