Investing.com - Oil prices continued to tumble on Friday, to hit the lowest level since 2009, as investors piled on to their short positions in anticipation of lower prices in the new year amid concerns over a growing supply glut.

On the ICE Futures Exchange in London, Brent for February delivery hit a session low of $55.48 a barrel, a level not seen since April 2009, before settling at $56.42, down 91 cents, or 1.59%.

On the week, the February Brent contract plunged $3.23, or 5.1%, the sixth consecutive weekly decline.

Elsewhere, on the New York Mercantile Exchange, crude oil for delivery in February slumped 58 cents, or 1.09%, on Friday to end the week at $52.69 a barrel, after hitting a daily low of $52.03, the weakest level since May 2009.

For the week, New York-traded oil futures sank $2.36, or 3.73%, the sixth straight weekly loss.

The spread between the Brent and the WTI crude contracts stood at $3.73 a barrel by close of trade on Friday, compared to $4.60 in the preceding week.

London-traded Brent prices lost nearly 48% in 2014, while WTI futures dropped almost 46% after the Organization of Petroleum Exporting Countries decided to maintain its output target at 30 million barrels a day.

The decision disappointed hopes the oil cartel would lower production to support the market, as a surplus develops amid the shale boom in the U.S., which is pumping at the fastest pace in more than 30 years.

In the week ahead, investors will be turning their attention to Friday’s U.S. nonfarm payrolls report for further indications on the strength of the recovery in the labor market. Wednesday’s Federal Reserve meeting minutes will be also closely watched.

The US dollar index, which measures the greenback against a basket of six major currencies, advanced 0.91% to nine-year peaks of 91.47. The index rallied 12% in 2014, boosted by the diverging policy outlook between the Fed and central banks in Europe and Japan.

Oil prices typically weaken when when the U.S. currency strengthens as the dollar-priced commodity becomes more expensive for holders of other currencies.