US crude tumbled below $40 per barrel for the first time since April as oil prices fell nearly 4 percent on Monday on heightened worries of an oil glut after a survey suggested OPEC output reached record highs last month,Reuters reported.
A Reuters survey on Friday found that output from the Organization of the Petroleum Exporting Countries likely rose in July to its highest in recent history as Iraq pumped more and Nigeria squeezed out additional crude exports despite militant attacks on oil installations.
Data on Friday also showed the United States added 44 new oil drilling rigs in July, the most for a month in two years, intensifying concerns that global production could once again get to unmanageable levels like in 2014-2015.