A convicted serial con man with a history of scamming car dealerships has been accused of perhaps his biggest scam yet: stealing at least seven vehicles from six dealerships in the Portland area in a single week.

Robert G. Steiner, 46, of Portland, known by police as “The Pretender,” was released two months ago from prison, where he served time for stealing three vehicles in 2001 from the Forest City Chevrolet dealership in Portland.

He was still on probation when police arrested him Thursday at Berlin City Nissan in South Portland on a charge of violating his probation.

Steiner is accused of using several fake names, fraudulent paperwork and elaborate stories to swindle car dealers who found him believable enough to sell him cars with no money down, on a promise that he would buy more cars.

At the time of his arrest, police in Portland, Scarborough, South Portland, Yarmouth, Westbrook and Saco were investigating complaints from dealerships that a man matching Steiner’s description had used aliases to persuade them to sell him new cars with no upfront cash or financing.

Portland police charged Steiner on Monday with two counts of felony theft and four felony counts of aggravated forgery, accusing him of stealing two cars from Berlin City Toyota on Riverside Street on June 2. Steiner is expected to appear in court to face the charges this week.

Portland police Lt. James Sweatt said Monday that he expects many more charges as police in Greater Portland file cases against Steiner and, possibly, more thefts are discovered.

“It’s definitely the largest car theft that we’ve been involved in,” Sweatt said.

Police have recovered seven stolen cars from locations where Steiner allegedly stashed them, including the parking garage at Maine Medical Center, a hotel parking lot and other private lots where they wouldn’t draw immediate attention from police. All of the cars were in good shape when they were found, Portland police said. Most have been returned to the dealerships.

Steiner, who is being held in the Cumberland County Jail in Portland, declined a request for an interview by the Portland Press Herald.

Steiner’s criminal record dates back decades in Maine, Colorado, Florida, South Carolina and his home state of Michigan.

He was convicted of auto theft in Michigan in 1987 and larceny and grand theft in Florida in 1998, according to records filed at the Cumberland County Courthouse in his 2001 case.

Portland Detective Barry Cushman, who led that investigation, recognized Steiner’s name as theft reports came in from Memorial Day weekend until Steiner’s arrest, Sweatt said.

In 2001, Cushman interviewed Steiner’s mother, Mary Steiner, who told him that her son “had done this all his life” and that he was a “pathological liar” with a long history of psychological problems, Cushman wrote in his 2001 report.

A message left at the Steiner home in Michigan was not returned.

Scarborough police Sgt. Richard Rouse said his department investigated the theft June 3 of a 2014 Volvo S60, worth $44,000 including tax and title, from Portland Volvo, where a man offered to pay for the vehicle outright. The man said he had to get a bank check for the transaction and was allowed to drive away in the car to get the money. He never returned.

Gary Caron, general sales manager at Rowe Ford in Westbrook, said Steiner tricked members of his staff into letting him drive off with a new 2014 Ford Escape on May 30 by telling a convincing story.

“Basically, he came in and said he worked for a large construction company and wanted to buy 10 cars off us,” Caron said. “This guy is good.”

Caron said Steiner used a fake name. Although he didn’t have a driver’s license on him, the sales staff put a temporary dealer plate on the Escape and allowed Steiner to take it.

“He came in the next day with our vehicle and (arranged to buy) two more vehicles. He wanted us to deliver them to Scarborough,” Caron said. “We put the brakes on because he still hadn’t paid us for the first car.”

After trying to reach Steiner for two days, Rowe Ford called police to report the vehicle stolen.

“He’s just running around scamming these dealers,” Caron said.

Tom Brown, president of the Maine Automobile Dealers Association, which represents 118 new car and truck dealers throughout the state, said Scarborough police contacted him Thursday and asked him to notify member dealers in York County and Greater Portland.

In late 2000, Steiner wrote letters to Forest City Chevrolet in Portland, now Quirk Chevrolet, expressing interest in buying cars for what he said was his company. A salesman responded without realizing that the address Steiner gave was the Maine Correctional Center in Windham, where he was serving time for a previous car theft, according to Cushman’s report.

When Steiner arrived at Forest City Chevrolet, he told the finance director that he was the vice president of a company he had inherited recently from his father, Steiner and Associates in Falmouth, and that the company was the buyer of the vehicles, Cushman wrote.

He took possession of a Chevrolet Impala and a Chevrolet Tahoe on Feb. 20, 2001, and returned a day later for a Chevrolet Blazer, the report says.

Steiner was convicted in that case in 2002, initially sentenced to serve only three years of a 10-year sentence. But he violated the terms of his probation after his release and was returned to prison until April 4 of this year, according to court and Department of Corrections records.

Earl Stewart, a Toyota dealer in Lake Park, Florida, who wrote “Confessions of a Recovering Car Dealer,” said dealerships are fiercely competitive and the sales incentive structure can lead them to take chances that might make them vulnerable to a con artist.

“You can make or break your month on the last day of the month,” he said. Meeting a sales goal can be worth tens of thousands of dollars, paid by a manufacturer to a dealership. The incentives are extended to individual sales people.

“If I’m a salesman with 14 cars out and a $5,000 bonus to sell the 15th, I’m very motivated,” he said. “Maybe take a chance that I’m really going to get paid.

“You have to want to make a deal real bad to let someone take the car and come back with the check,” he said, but he was not surprised that dealerships got scammed.

“I’ve lost cars. I’ve lost money,” he said. “I’ve been in business since 1968 and I could write another book just on the dumb things I did.”