The US coast guard confirmed today that a well in the Gulf of Mexico is leaking light oil and natural gas. The oil has reportedly formed a sheen about four miles long and three-quarters of a mile wide on the surface of the Gulf. Five workers on the well platform, Ship Shoal Block 225 Platform B, which is owned by Energy Resource Technology, were safely evacuated.

Oil accidents in the Gulf are of course a sensitive topic ever since BP’s Macondo disaster in 2010, which is now the subject of a bitter dispute about compensation claims. The specific causes of the leak are unknown, but the Coast Guard described it as a “loss of well control.” According to the Bureau of Safety and Environmental Enforcement (BSEE), which requires that all such incidents be reported to it, they have become less common than they used to in the Gulf of Mexico of late, but still happen three to four times a year:

A loss of well control doesn’t necessarily mean any oil is spilled, and when it is, the quantities may be tiny. In 2011 and 2012, all the reported loss-of-well-control incidents combined spilled just over 30 gallons of oil into the sea, according to BSEE’s data.

There is no information so far on how much oil has been spilled in today’s episode. According to the blog Fuel Fix, the workers were plugging up the well and preparing to abandon it permanently after 15 years of inactivity when the leak was discovered.