BP says the "static kill" of its ruptured Gulf of Mexico oil well has worked, a big step towards sealing it.
In the procedure, special drilling fluid known as mud is pumped in the well, forcing the oil back down.
BP said well pressure was being controlled by the hydrostatic pressure of the drilling mud, which was "the desired outcome".
The well is being monitored, and further pumping of mud could be necessary, it added.
BP began pumping mud into the well from vessels on the surface at 2000 GMT on Tuesday, in order to counter the pressure from the oil pushing out of the reservoir below the seabed.
The company could eventually seal the mouth of the well with cement.
The US government says the well leaked 4.9 million barrels of oil before being capped last month, with only 800,000 barrels being captured.
The well ruptured after an explosion on a drilling rig in April which killed 11 workers. The flow ended on 15 July, when BP closed a new cap it had put on the well.
