Electric car specialist Tesla has announced a US$3.6 billion (AU$5.2 billion) investment in two new plants in the US state of Nevada to ramp up production of its semi-truck and more battery packs for its passenger cars.

The new factories will be added to Tesla’s Gigafactory Nevada site in the US, which has reportedly built 1.5 million battery packs for the company’s electric cars since it opened in 2016.

The Tesla semi truck — unveiled as a concept in 2017 before going into production late last year after several delays — is currently in limited production at the company’s Texas plant.

However, the new multi-billion dollar facility in Nevada will be Tesla’s “first high-volume semi-factory,” according to the company.

No production figures were provided for the new semi factory, but Tesla previously announced a goal to produce 50,000 semi trucks for North America by 2024.

Meanwhile, the new semi-truck factory will be complemented by a facility that produces “4680” batteries for Tesla passenger vehicles, which the company says will be able to produce 100 GWh of batteries per year — enough for two million cars and SUVs.

The “4680” cells — also in production at Tesla’s Texas plant — are currently only used in some Tesla Model Y SUVs sold in the U.S., but are set to expand to this year’s Tesla Cybertruck, which is slated to begin production mid-year .

Tesla says the two additional plants in Nevada will employ 3,000 new workers.

The electric car giant’s Gigafactory Nevada joins vehicle assembly plants around the world — Fremont, California and Austin, Texas in the US, Shanghai in China and Berlin in Germany — as well as smaller facilities elsewhere to manufacture electric car chargers, vehicle parts and battery packs for home.