New York State Attorney General Eric T. Schneiderman has sent letters seeking tax and other financial records from close to two dozen registered “social welfare” groups, escalating his office’s inquiry into politicking by nonprofit organizations, according to The New York Times.

Both Republican- and Democrat-linked 501(c)(4) organizations have received the requests. The move comes amid heightened tension over such groups, which are spending tens of millions of dollars on attack ads in the 2012 election cycle but maintain that their primary activity is educational and not political, and thus that they are not required to disclose their donors.

Under New York law, tax-exempt groups that do business or raise substantial funds in the state must submit auditor’s reports and their U.S. tax returns to the attorney general’s office. With New York City a major hub of political fundraising, that regulation could give Mr. Schneiderman some jurisdiction over the 501(c)(4) groups such as Karl Rove’s Crossroads GPS or Priorities USA Action, which was founded by former Obama aides.

The Times reported in June that the attorney general was examining the financing of politically active nonprofit entities, focusing on a case involving the U.S. Chamber of Commerce.