Massachusetts on Friday subpoenaed four brokers to obtain sales, revenue and training records for leveraged exchange-traded funds: Ameriprise, UBS, LPL and Edward Jones.

However, Amerprise, UBS and LPL had already suspended or curtailed sales of the products in recent weeks, apparently responding to investigations by the Financial Industry Regulatory Authority and Massachusetts into the products. Charles Schwab last week warned investors about the products, and Morgan Stanley Smith Barney is reviewing sales of the products.

Due to the heightened volatility of the stock market over the past year, 55% of leveraged ETFs and 88% of inverse ETFs have delivered the opposite performance of what they are designed for, The Wall Street Journal reports, citing Morningstar data. Thus, as Morningstar Director of ETF Analysis Scott Burns told the paper, the performance of leveraged and inverse ETFs becomes somewhat “less trustworthy.”

Regulators are concerned that investors may not understand or fully appreciate the products risks, since the number of these funds has increased 86% over the past year and a half to 119 with $32.8 billion in assets, up from $11 billion at the start of last year. Regulators attribute the strong growth to aggressive marketing.