BUENOS AIRES, March 23 (Reuters) - Miners Enirgi Group Corporation and Orocobre will expand their production of lithium in Argentina with investments of $720 million and $160 million, respectively, Argentina's government said on Thursday.

Argentina is the world's No. 3 producer of lithium, a hotly demanded material used in car batteries and mobile phones.

According to the government's statement, the investment from Enirgi to create an advanced materials division in Argentina will help the company increase its production to more than 50,000 tonnes of lithium carbonate annually.

Enirgi Group said in a March 21 statement it was opening an advanced materials division in Argentina but did not give an investment amount.

Orocobre's production would increase to 30,000 tonnes per year in 2020 from 13,000 tonnes currently, the statement said.

The companies did not immediately respond to request for comment.

Industry representatives and the government say Argentina's lithium production could triple by 2019 as companies announce investments.

Currently, Argentina produces 29,000 tonnes of lithium carbonate per year, around 15 percent of global output.

(Reporting by Nicolas Misculin and Caroline Stauffer; Editing by Leslie Adler)