There’s been a lot of counterfeit money passing through Winchester businesses in recent weeks and police think most of it is related to the illegal drug trade.

“The vast majority (of fake bills) we’re getting have the same serial number,” Winchester Police Capt. James Hall said. “We probably had 15 (bills) in a two- to three-week period. Of that, 75 percent had the same serial number.”

Instead of a usual counterfeiter passing one bill at a time after purchasing a small item, some of these were turning up with authentic bills as well. Some people or businesses didn’t know they had bad money until long after they accepted the bill, he said.

The phony money is likely not all coming from the same source, he said, as quality has varied among some of the bills.

“Some say ‘for movie use only,’” Hall said. “Some has been decent quality.”

Police arrested several people for criminal possession of a forged instrument after allegedly passing the bills.

“We have tracked some of the people down that passed them,” he said. “They knew they were counterfeit. We think there’s an original source. We don’t think they were manufacturers. If its big enough, we’ll bring in the Secret Service.”

In the meantime, businesses and residents should watch what money they accept and hand out more closely, he said.

Many businesses use special pens to identify counterfeit money and some are using money readers as well.