U.S. electric car manufacturer Tesla Motors is in discussions with German automaker BMW over a possible collaboration in batteries and lightweight components.

During an interview published on Sunday, Tesla CEO Elon Musk described BMW's production of carbon fibre reinforced car body parts as "interesting" and "relatively cost efficient," according to Reuters.

"We are negotiating with BMW in connection with new technology for batteries and charging stations as well as technologies for the production of carbon fiber, which is important to our engineering department," Musk was quoted as saying in the interview with German weekly Der Spiegel.

BMW made no official comment regarding Musk's statements this weekend.

BMW uses carbon fibres from its joint venture with materials manufacturer SGL to make reinforced passenger cell parts for its i3 electric hatchback and i8 plug-in hybrid sports vehicles.

A spokeswoman for Tesla in Germany described the discussions as "informal," however.

"The conversation between Elon Musk and BMW has been a casual conversation, and not about a formal cooperation," spokeswoman Kathrin Schira said, according to Reuters.

There were no further details released regarding a partnership, though Tesla and BMW executives reportedly met back in June to discuss the creation of charging stations useable for different types of electric vehicles.

Rival automaker Daimler, which owns the Mercedes brand, announced last month that it would collaborate with Tesla even after selling off its remaining four percent stake in the Model S maker.

Tesla has also worked in the past with Toyota on its electric SUVs.

The company's billionaire co-founder Musk also said to Der Spiegel that he plans on having a battery production plant in Germany sometime in the next five to six years.

Earlier this year, Musk said the "wall" of Tesla's patents in the lobby of its Palo Alto headquarters had been removed in the "spirit of the open source movement, for the advancement of electric vehicle technology."

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