Hundreds of small investors who put money into renewable energy projects via crowdfunding site Duurzaaminvesteren.nl are facing heavy losses as one project after another runs into financial trouble, Dutch media reported on Thursday.

The platform, one of the biggest of its kind in the Netherlands, raised nearly €400 million in the past decade for solar farms, battery systems, charging stations and start-ups.

But a growing number of projects have defaulted on payments, prompting angry investors to organise themselves into a pressure group which now has some 1,500 members, according to the Telegraaf.

Many investors say they believed they were spreading their risk by backing multiple projects, but later discovered that several were linked to the same parent company, Trio Investment.

According to the Telegraaf, Trio controls dozens of companies at the same address, raising concerns it operates as a “pyramid scheme.” The company did not respond to requests for comment.

Complaints are also mounting over how Duurzaaminvesteren has presented the risks. On Trustpilot, investors accuse the platform of painting too rosy a picture by publishing a default rate of 6.9% across all projects, while many report that half or more of their own portfolios are in difficulty.

“Even a casino is more profitable,” one investor wrote. Another told the Financieele Dagblad: “What is happening here goes far beyond normal investment risk.”

Duurzaaminvesteren’s chief executive, Hans van der Pouw, told the FD that the number of payment delays is “much too high” but blamed fast-changing market conditions, such as the collapse in battery prices due to Chinese competition.

He said only 1.7% of all projects have gone bankrupt and promised more transparency, including automatic updates to statistics and the introduction of a risk score for new projects.