Dutch prosecutors said on Oct. 12 they will pursue a pollution case against NAM, a joint venture of Shell and ExxonMobil that operates gas fields in the Netherlands.

The prosecutors "[suspect] NAM of injecting waste streams from natural gas extraction into the deep subsurface without a permit," a statement from their office said.

Prosecutors say they believe the company took waste products from natural gas extraction in the North Sea, then processed and injected them into empty gas fields in the province of Groningen.

A spokesperson for NAM said the company would respond later on Oct. 12.

Reuters reported last month that Shell And ExxonMobil have put their 50:50 venture up for sale, with expected proceeds of over $1 billion.

NAM started producing natural gas in 1963 following the discovery of the giant Groningen field, which was a major source of gas for the Netherlands and Europe for decades.

But extraction has been almost completely wound down in the past 10 years as tremors blamed on drilling damaged buildings and prompted protests by residents and campaigners.

Production at Groningen has been capped at 2.8 Bcm in a year, down from 4.5 Bcm.