"We have no concrete evidence. But hopefully we will," Stenling told the New York Times.
The counterintelligence chief announced the lack of evidence after the decision of the Swedish government to keep the probe's details secret reportedly prompted "speculations" of the Western states that Sweden had presumably solved the case and remained silent about the results, according to the newspaper.
He added that the "entire investigation is unusual," as quoted by the newspaper.
On September 26, fuel leaks were registered on the Nord Stream 1 and Nord Stream 2 pipelines. The causes of the incidents have not yet been established. The operator, Nord Stream AG, reported that the damage was unprecedented and it was impossible to estimate the time frame for repair work. The Russian Prosecutor General's Office is investigating the pipeline incidents as acts of international terrorism. The European Union has also launched a probe into the incidents.