Regulators from several states are investigating a data breach from a subsidiary of the credit-tracking behemoth Experian.

The investigation by attorneys general in these states concerns whether the subsidiary adequately secured some 200 million social security numbers and whether victims were properly notified. The investigation, first disclosed by Reuters, comes as the Obama administration is pressing for legislation requiring companies to better secure customer data.

A Vietnamese man who operated a website, called findget.me, offering social security numbers has pleaded guilty to charges that he obtained the data from the Experian subsidiary, Court Ventures. The firm, a court document retrieval service, also jointly maintains a database of some 200 million social security numbers with another firm.

Hieu Ngo, who is to be sentenced in New Hampshire federal court in June, posed as a foreign investigator and conducted more than 3 million queries on the database during a nine-month period ending in 2012 before being cut off, according to court documents.

It is not clear how many social security numbers were accessed.

A spokeswoman for Illinois Attorney General Lisa Madigan described the probe as a “multistate investigation” that includes Connecticut and other states.

Experian said in an e-mail that it was "treating the matter seriously" and that Ngo was hijacking the data "before Experian acquired the assets of Court Ventures."

Illinois and Connecticut are also examining the recent Target breach, in which as many as 40 million credit card numbers were hijacked from the retailer.