Silicon Valley investors are known for pouring money into risky bets like flying cars and asteroid mining. Now, a handful are diving into one of the few industries that makes most of their peers squeamish — pot.

As the marijuana industry soars, with New Frontier Data predicting legal pot sales will balloon to more than $24 billion by 2025, a handful of venture capitalists are climbing on board — albeit cautiously. Those putting money into the industry say it’s a rare chance to stake an early claim in a lucrative market with little competition from other investors. But they’re keeping one eye on President Donald Trump’s administration, watching for signs of a federal crackdown that could derail the burgeoning industry.

“It’s a completely untapped market with huge opportunity,” said Tusk Ventures Founder and CEO Bradley Tusk, an investor in San Francisco-based marijuana delivery darling Eaze.

For Tusk Ventures, a VC firm that specializes in helping startups like Uber and FanDuel navigate complex regulatory landscapes, the controversial marijuana industry seemed like a natural fit. The firm is considering a second investment in the space.

And it’s not alone. DCM Ventures, a 21-year-old VC firm with an office on Sand Hill Road, also invested in Eaze, as did Fresh VC and the Winklevoss twins — the brothers who made headlines by claiming they came up with the idea for Facebook. Other investors dabbling in pot companies include prestigious Mountain View-based startup accelerator Y Combinator, Peter Thiel’s Founders Fund and New York City-based Lerer Hippeau Ventures — which also backs big names like Soylent, which makes meal-replacement drinks and bars popular among Silicon Valley techies, and Venmo, a mobile payments platform.

Industry insiders say there’s been a slow uptick in interest. Investors have poured nearly $30 million into marijuana-tech startups — companies that sell marijuana-related technology or use tech to sell cannabis products — so far this year, according to PitchBook Data. That means 2017 is on track to beat last year’s total of $49 million. But much of that money is coming from niche firms created exclusively to fund cannabis-related businesses, such as Phyto Partners and Poseidon Asset Management.

Despite the marijuana industry’s massive potential, interest from Sand Hill Road has amounted to more of a trickle than a flood. Though California voters approved recreational marijuana use last November, and lawmakers are working on crafting regulations to allow sales to start next year, the plant remains illegal on the federal level. That leaves most VCs unwilling to venture into the industry. Many venture capital firms are forbidden from entering the space by agreements with their limited partners — the pension funds and other institutions that supply the VCs’ investment capital.

“This is a no-go area for traditional venture funds, at least for now,” said Venky Ganesan, chairman of the board of the National Venture Capital Association and managing director of Menlo Ventures.

While mainstream VCs hesitate, a crop of investment firms specializing in marijuana have sprung up to fill the void. Groups like Los Angeles-based Casa Verde Capital, backed by rapper Snoop Dogg; and Gateway, an Oakland-based incubator for cannabis startups, can take much of the credit for keeping the marijuana tech industry afloat.

Pranav Sood, whose Oakland-based startup Trellis sells inventory management software to cannabis growers and distributors, recently turned to the industry’s niche investors after striking out with mainstream VCs.

“It quickly became apparent that more traditional VCs are not really getting into this space,” he said. “That’s when we kind of shifted focus as well. It was a pretty quick lesson learned.”

Trellis is closing its first round of funding, which will bring in $2 million from a group of investors led by Casa Verde. Sood said investor sentiment toward the marijuana industry has been volatile — spiking as support grew for legalized recreational marijuana, dropping with Trump’s arrival in office, and picking back up recently.

“Honestly, it’s been a little bit of a roller coaster,” he said. “On any given day, you don’t know how an investor’s going to feel.”

Brian Sheng, a partner at Fresh VC, said his firm was drawn to Eaze partly because the startup never actually touches marijuana — Eaze only provides the online platform that connects dispensaries with customers. That cuts down on the risk, Sheng said.

Private equity also is expanding into marijuana. MedMen, a Los Angeles-based firm that manages companies in the cannabis space, launched its first marijuana-focused private equity fund last summer, which now controls almost $100 million in assets. The firm also held its first investment conference last month, drawing more than 300 people interested in putting their money into the marijuana industry. So far the cash going into these types of funds has mostly been from wealthy individuals and families, MedMen Co-Chairman Chris Leavy said, but pension funds, endowments, foundations and other institutional investors are starting to show interest.

“Access to capital for this industry is slowly improving,” Leavy said. “Wherever you look, you can see signs that the investor interest is broadening.”