A recent report by New York Attorney General Barbara D. Underwood’s office indicates some cryptocurrency exchanges are vulnerable to manipulation, a finding that some market observers believe could be a blow to bitcoin exchange traded funds winning regulatory approval.

Last month, nine Bitcoin-based exchange-traded fund (ETF) applications got the thumbs down from the Securities and Exchange Commission on Wednesday, preventing the digital currency from gaining more acceptance from investors who are wary of the unregulated exchanges of cryptocurrencies. The SEC’s Division of Trading and Markets rejected applications from investment firms ProShares, Direxion and GraniteShares.

The SEC stated, “Among other things, the Exchange has offered no record evidence to demonstrate that bitcoin futures markets are ‘markets of significant size.’ That failure is critical because, as explained below, the Exchange has failed to establish that other means to prevent fraudulent and manipulative acts and practices will be sufficient, and therefore surveillance-sharing with a regulated market of significant size related to bitcoin is necessary.”

Related: A Concerning Bitcoin Price Prediction

Earlier this year, the New York attorney general’s office unveiled the Virtual Markets Integrity Initiative in an effort to bolster accountability and transparency across the cryptocurrency platforms retail investors use.