The United States Securities and Exchange Commission (SEC) has issued a Wells Notice to the popular trading platform Robinhood.

Following the news of the Wells Notice, Robinhood (HOOD) share price fell 2.5% in pre-market trading, to $17.95 as of 12:50 pm UTC. The Wells notice was issued on May 4, according to court filings.

The Wells notice is a letter sent from the securities regulator that concludes the conclusion of its investigation over the respondent, in this case, Robinhood’s United States-based crypto business.

According to the filing, the SEC has been investigating Robinhood’s cryptocurrency listings, crypto custodian operations and made the “preliminary determination” to recommend that the SEC file an enforcement action related to alleged securities violations.

The news of the investigation comes despite Robinhood’s attempts to register with the United States securities watchdog, according to Dan Gallagher, chief legal, compliance, and corporate affairs officer at Robinhood Markets.

Gallagher wrote in a May 6 blog post:

“After years of good faith attempts to work with the SEC for regulatory clarity including our well-known attempt to ‘come in and register,’ we are disappointed that the agency has decided to issue a Wells Notice related to our U.S. crypto business.”

Gallagher added that Robinhood doesn’t see any of its listed assets as securities:

“We firmly believe that the assets listed on our platform are not securities and we look forward to engaging with the SEC to make clear just how weak any case against Robinhood Crypto would be on both the facts and the law.”

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This is a developing story, and further information will be added as it becomes available.