Securities regulators are investigating whether JPMorgan Chase & Co. misled investors in its April earnings statement by failing to disclose a change in how it measured risk, Securities and Exchange Commission Chairman Mary Schapiro said on Tuesday.

"Part of what we are investigating is the extent of that disclosure and whether it was adequate, among other things," Schapiro told lawmakers during a House Financial Services hearing.

Schapiro's comments were the first time she said explicitly that the SEC is focusing on what the bank disclosed and what Chief Executive Jamie Dimon said on April 13 after news reports about rising risk at the bank's Chief Investment Office, which turned out to have lost at least $2 billion trading credit derivatives.

By omitting any mention of model change from its earnings release in April, the bank disguised a spike in the riskiness of a particular trading portfolio by cutting in half its value-at-risk number.

Tuesday was the second time that U.S. financial regulators, as well as Dimon, have appeared before lawmakers to answer questions about the failed hedging strategy.

Schapiro said on Tuesday that although companies are not required to disclose such a model changes in their earnings releases, other SEC rules still require such statements to be truthful and complete.

The agency is looking at the disclosure in light of the fact that it came at the same time that Dimon called reports about heightened risk at the CIO office a "tempest in a teapot," Schapiro said.

"If you chose to speak, you absolutely must speak truthfully and completely and not allow yourself to leave any kind of misleading impression from the information that you are putting out," Schapiro told the lawmakers.

"The duty under Federal securities laws is to speak completely and truthfully," she said.

Dimon made the "tempest in a teapot" comment in a conference call with analysts the day the bank issued the low-risk reading as the company reported first quarter earnings on April 13.

Dimon told a Senate Banking Committee hearing last week that he was "dead wrong" when he dismissed the reports of trouble and that, at the time, he had not focused on the model change.