The price of a barrel of Brent crude oil has slipped below the $60 mark again, after a survey by the American Petroleum Institute showed inventories had risen by 14.3m barrels last week. That's against expectations of 3.2m barrels.
The shock rise goes against figures by oilfield services firm Baker Hughes, which showed the number of rigs in operation in the US fell to 1,056 in the week to 13 February.
The price of Brent crude has risen in recent weeks from the six-year low of $45.19 it hit in mid-January, as forecasts suggested supply would begin to dwindle.
But its price fell back by $1 yesterday after analysts voiced their concerns that the global supply glut was here to stay.
Steve Sawyer, an analyst at Facts Global Energy, warned that the market is "still fundamentally oversupplied... we expect oil prices to come off during March and April... but it's a roll of the dice by how much".