The number of rigs drilling for oil and natural gas in the US has fallen to the lowest level since at least 1940, oil services company Baker Hughes Inc said, The Wall Street Journal reported.

The number of combined rigs in the US oil and gas fields fell by nine during the second week of March to 480, overwriting a previous record low of 488 in April 1999, according to the closely-followed industry data. Oil rigs alone fell for a 12th week in a row with the rig count down six to 386, the lowest level since December 2009. Meanwhile gas rigs fell by three to 94, the least since at least 1987.

This movement comes as the energy firms continued to slash activity amid the deepest energy price rout in a generation and, according to CNN, it is a reflection of the dramatic downturn in the US energy industry caused by excess supply.

Last month, oil prices plunged to a 13-year low of $26 a barrel, even though they have recently bounced back to $39. Natural gas prices remain near 17-year lows.

Still, many analysts think the rig count will rebound later this year with signs that oil prices had bottomed in the last month after US crude hit a 12-year low of just around $26 a barrel, Reuters reported.

In spite of the decline, actual production has been surprisingly resilient, mainly because oil companies have been getting more out of existing fields and are focusing on their most economic projects. Domestic production has also been boosted by strong output from deepwater projects in the Gulf of Mexico.