SHANGHAI (Reuters) – Tesla Inc Chief Executive Elon Musk has told his staff it was time to bring the Tesla Semi commercial truck to “volume production,” a message that coincides with a surge in the share price of rival clean truck maker Nikola Corp.

Musk, in an email seen by Reuters on Wednesday, did not specify a timeframe for ramping up production of the Semi.

“Production of the battery and powertrain will take place at Giga Nevada,” Musk wrote. Most of the other work will probably take place in other states, he wrote, without stating where.

Musk has said Tesla is scouting other U.S. states for a site to build a new factory, hinting that Texas could be a candidate. Oklahoma and other states are campaigning for the investment.

Tesla did not immediately respond to a request for comment.

When Musk unveiled the prototype of the futuristic, battery-powered Semi in 2017, he said the Class 8 truck would go into production by 2019. More recently, he said the Semi would go into volume production by 2021.

Nikola, a rival electric and fuel cell truck startup, earlier this month began trading on the NASDAQ after it merged with special purpose acquisition company VectoIQ.

Shares in Nikola have more than doubled in price over the past week as the company’s CEO has used Twitter and interviews to promote plans to launch an electric pickup truck to rival Tesla’s forthcoming Cybertruck.

Nikola and CNH Industrial’s IVECO commercial truck operation last year formed a joint venture to build a battery electric and fuel cell truck line called the Nikola Tre. IVECO has said orders are strong for the electric version of the truck, due out next year.

Nikola on Wednesday said it had hired a former Tesla executive, Mark Duchesne, to lead its manufacturing and a former Caterpillar executive, Pablo Koziner, to head its hydrogen fueling and battery recharging business.