MOSCOW (AP) — Russian energy giant Gazprom on Friday raised the possibility of a prolonged halt of natural gas supply through a key pipeline to Germany, citing the need for urgent maintenance work.

The Russian state-run energy company said in a social media post that it had identified “malfunctions” of a key turbine along the Nord Stream 1 pipeline, which carries natural gas from Western Russia to Germany. It said the pipeline will not work unless these are eliminated.

Early on Wednesday, Gazprom completely halted the flow of gas through Nord Stream 1, in line with an earlier announcement, adding that the stoppage would last for three days.

The company said work was necessary on the only remaining functioning turbine at the Portovaya compressor station at the Russian end of the pipeline but German officials cast doubt on that explanation.