LONDON (TIP): Oil prices extended their retreat Thursday after hawkish US Federal Reserve meeting minutes strengthened the dollar and a weekly report showed rising US crude stockpiles.

Prices hit 2016 highs Wednesday due in part to production outages resulting from wildfires around the Canadian oil sands hub of Fort McMurray but pulled back to settle lower after the dollar climbed.

A stronger greenback makes dollar-priced oil more expensive, denting demand and hurting prices.

Minutes from the US Federal Reserve’s policy meeting in April that were released Wednesday showed that policymakers kept open the door to raising interest rates in June. Higher interest rates typically encourage investors to move to the dollar for higher yields, lifting the currency.

At about 1200 GMT, US benchmark West Texas Intermediate (WTI) for June delivery was down 84 cents at $47.35 per barrel. Brent for July dipped $1.08 to $47.85 a barrel. “The main factor weighing on prices is the much appreciated US dollar,” said Commerzbank analyst Carsten Fritsch.