U.S. regulators and trading venues are still looking into last week’s unexplained market plunge, and contemplating trading safeguards in response.

The U.S. Securities and Exchange Commission said that Mary Schapiro, SEC chairman met with the leaders of six exchanges — the New York Stock Exchange, NASDAQ, BATS, Direct Edge, ISE and CBOE — Monday, and the industry self regulator, the Financial Industry Regulatory Authority, to discuss the causes of last Thursday’s market events, the potential contributing factors, and possible market reforms.

“As a first step, the parties agreed on a structural framework, to be refined over the next day, for strengthening circuit breakers and handling erroneous trades,” the SEC said.

Over the weekend, the two biggest exchanges, the NASDAQ OMX Group and NYSE Euronext, said that they are committed to working closely with each other, the SEC, and other regulators to determine the cause of the sudden market plunge, and to develop effective solutions promoting greater market stability, efficiency and transparency.

However, as yet, that plunge, which has been attributed to everything from erroneous trades to high-frequency traders, and unanticipated glitches in the interaction of various trading venues, has not been conclusively explained.

IE