The Minnesota Department of Revenue announced that as of 3 p.m. Saturday it is again accepting tax returns submitted using TurboTax.

The state had stopped accepting TurboTax-prepared returns Thursday after a few taxpayers tried to file and received a message that their return already had been submitted. Revenue officials suspended those returns and launched an investigation into potentially fraudulent activity.

The department quickly established that its own antifraud measures were operating effectively.

"There was never a question about a breach in our software system; it seemed to be a problem with that particular software," said Cynthia Bauerly, Minnesota's commissioner of revenue.

Intuit, the California-based company that owns TurboTax, also temporarily stopped filing state tax forms Thursday after noticing what it described as "an increase in suspicious filings and attempts by criminals to use stolen identity information to file fraudulent state tax returns and claim tax refunds."

Working with a third-party security firm, Palantir, Intuit said Friday that it was confident there was no security breach in its systems. To prevent further problems, Intuit implemented new authentication measures specifically designed to prevent identity theft.

It also set up a toll-free line, 1-800-944-8596, for TurboTax customers to call if they suspect fraud.

Minnesota officials are continuing to review taxes submitted via TurboTax and will contact anyone whose forms raise concerns or show signs of fraud.

"If people believe they have been affected, or if they log into their TurboTax account and find they've already been filed, they should contact the IRS and the state they're filing in," Bauerly said. "In Minnesota, if they've already filed and used TurboTax, there is nothing they need to do at this time. If there is a problem, we will contact them."

Minnesota continues to "encourage electronic filing," Bauerly said, adding that "it's back to normal." â–¡

Mary Abbe • 612-673-4431