The German government has dropped a formal investigation into allegations that the NSA had been tapping chancellor Angela Merkel's phone for several years. German federal prosecutor Harald Range said in a statement on Friday there was insufficient evidence to continue the investigation, The New York Times reports.

Back in 2013, German newspaper Der Spiegel ran a report claiming the US had been monitoring Merkel's phone since 2002, based on internal NSA documents it had obtained. The White House responded by assuring Merkel she was no longer being monitored, but the report suggested the surveillance had gone on for more than a decade.

No proof it was an "authentic" order

Range noted that while the NSA documents did contain a phone number that could be traced back to Merkel, there wasn't enough evidence to suggest there had been an "authentic" order from the NSA to tap the phone. He also said there wasn't enough evidence to prove Merkel's phone had actually been tapped.

"It was possible to determine that the telephone number listed is assigned to a mobile telephone used by the chancellor," Range said, according to the Times. "The data on the document otherwise remain open to various interpretations."

Range began a formal investigation into the claims in June of last year, following pressure from the German Parliament. Despite pushback from European leaders against the NSA's less-than-palatable surveillance tactics, President Obama has remained relatively neutral on the topic. In a meeting with Merkel this February about US surveillance practices, Obama reportedly said, "I would like the Germans to give us the benefit of the doubt."

"The vague remarks from US officials about US intelligence surveillance of the chancellor’s cellphone — i.e. ‘not any more’ — are insufficient evidence," Range said, according to the Times.

Investigators are still looking into claims that the German surveillance agency BND fed sensitive data to the NSA, and claims that American and British spy agencies have been monitoring German citizens.