Tesla Will Probably Break Ground On Its First Gigafactory Next Month, But Still Won't Say Where

REUTERS/StringerElon Musk, CEO of Tesla Motors, waves during a news conference to mark the company's delivery of the first batch of electric cars to Chinese customers in Beijing April 22, 2014.

Tesla CEO Elon Musk said Wednesday evening he hopes to break ground on the company's first Gigafactory as early as next month, but that the company is still deciding where to do so.

In the firm's Q1 earnings call, Musk also added California is now back in the mix of potential sites for the battery factory, but added it may be too late. Arizona, Nevada, New Mexico and Texas are all said to be in the running.

The firm announced in February it would begin building Gigafactories to produce electric batteries for both its cars and for solar power systems - Musk is chairman of solar service firm SolarCity. Musk announced on the call that the firm had signed a letter of intent with Panasonic to partner with the electronics giant to supply parts for the factory, and anticipated a final agreement would come at the end of the month. There has been uncertainty about whether Panasonic was completely on board with the project.

Shares were down 7% after hours.