Oil company BP's ruptured oil well showed no signs of leaking on Friday after a new cap stopped crude from flowing into the Gulf of Mexico.
BP was conducting a pressure test and underwater robots were scanned the sea floor for signs of oil leaks.
Senior vice president Kent Wells said pressure within the well is steadily rising, a good sign.
President Barack Obama cautiously welcomed the news but added there was more work to do before the well was permanently stopped.
It was the first time BP managed to cap the flow since the explosion on 20 April that killed 11 workers.