Boring Company had launched its commercial tunnel project in Las Vegas last June to transport visitors through the city’s Convention Center using human-driven Tesla vehicles.

Elon Musk’s The Boring Firm has secured $675 million in a Series C investment round, valuing the tunnelling company at $5.675 billion, the company announced on Wednesday, adding that the cash will be used to increase employment across industries.

The Austin, Texas-based company said the funding round was led by Vy Capital and Sequoia Capital, with participation from Valor Equity Partners, Founders Fund, 8VC, Craft Ventures, and DFJ Growth. It plans to expand its workforce in engineering, operations, and production to scale up its Loop projects.

Musk, who also runs electric car manufacturer Tesla Inc and rocket business SpaceX, wants to revolutionise transportation by transporting people in pods through a hyperloop interstate system of gigantic subterranean vacuum tubes.

Musk has raised cash by selling Boring Company hats and flamethrowers.

Last week, billionaire Elon Musk launched a $43 billion cash buyout bid for Twitter Inc. His bid price of $54.20 per share represented a 38% premium to Twitter’s closing on April 1, the penultimate trading day before his 9.1% stake in the social media company was made public.

Boring Co.’s goal is to “solve traffic” by constructing transportation networks in deep subterranean tubes. The business already has a tunnel system in place at the Las Vegas Convention Center and carried passengers around earlier this year for the CES convention. The firm intends to grow into additional locations in the future years and stated that the extra money would be used to “significantly increase hiring.”

Boring has changed from its inception in 2016, when its ambition was long-distance transit spanning hundreds of kilometres. It now focuses in shorter travels within cities, some of which are simpler to work in than others. Projects in Chicago, Los Angeles, and a link between Washington and Baltimore have all fallen through, despite the fact that the Vegas project has received praise.

Valor Equity Partners, Founders Fund, 8VC, Craft Ventures, and DFJ Growth are among the other investors in the round. Boring Co. secured $120 million in funding three years ago at a value of $920 million.

In a blog post, Sequoia Capital’s Shaun Maguire stated that Boring’s “technology is now beyond the state-of-the-art, and improving at an exponential rate.”

Musk has a lengthy history with Sequoia., an early Musk firm that handled online payments, was sponsored by Sequoia’s Mike Moritz, but when the company merged with another startup and became PayPal, Musk was ousted as CEO due to management differences. Roelof Botha, a Sequoia partner, formerly served as PayPal’s chief financial officer.