BP has succeeded in stopping its Gulf of Mexico leak for the first time since an accident on April 20 killed 11 men and triggered a giant oil spill, boosting the shares.

The company on Thursday begun a “very, very intricate operation” aimed at sealing the gusher, the day after a leaking valve caused operations to be delayed.

It stopped the oil leak after only a couple of hours, having predicted that it might take up to two days for the flow to come to a halt. The company had worried that deepwater pressure could cause more ruptures, worsening the situation.