The State Patrol said it has launched a criminal investigation into the bankrupt Denny Hecker Automotive Group, dealing a new blow Wednesday to the man who was one of Minnesota’s largest car dealers until the economic downturn brought down his empire.

The chief of the State Patrol, Col. Mark Dunaski, said at a news conference in the Minneapolis suburb of Golden Valley that dozens of customers in 15 Minnesota counties have reported that they never received the titles or license plates for the vehicles they bought. He said they’ve also complained that they traded in vehicles only to learn later from their old lenders that the liens were never paid off.

Authorities searched Hecker’s corporate headquarters in the Minneapolis suburb of St. Louis Park, as well as several vehicles in the parking lot, three of his homes and two dealerships for paper or electronic evidence about the transactions, Dunaski said.

Hecker has not been charged and does not face imminent arrest, Dunaski said.

Dunaski also said it was far too early to estimate how much tax money was not paid to the state.

Defense attorney Marsh Halberg said Hecker was “a little shell-shocked” by the latest developments.

“This comes as a surprise to everyone involved, for Denny and the corporation,” Halberg said.

Halberg said Hecker was at his headquarters and that he and his staff were fully cooperating with the search, supplying computer passwords and handing over files.

Halberg said lender GMAC, not Hecker, is to blame. Bill Mohrman, a corporate attorney for Denny Hecker Automotive, said since early this year, GMAC has controlled several dealerships and failed to pay the state for tax, title, and license fees.

Mohrman said Hecker’s company has been urging GMAC to pay the funds since March.

GMAC spokesman Michael Stoller denied the company would be involved in trades, lien payments or payment of state fees. Stoller said in a written statement that the dealership is responsible for paying such fees.

The Department of Public Safety agreed with GMAC.