SOUTH PHILADELPHIA (WPVI) -- Officials are warning about counterfeit cash being circulated around the region.One businessman in particular found out the hard way when he learned a lot of the money he took from customers turned out to be bogus.Vincent Emmanuel is frustrated with what's been happening over the last two weeks at his 7-Eleven store at 23rd Street and Passyunk Avenue in South Philadelphia."All of a sudden, we saw a surge of counterfeit $20 bills and $100 bills in the store," said Emmanuel. "They look almost real, but at the same time they're not real."The money looks real enough, and it wasn't until the bank notified Emmanuel that he realized some of the money he had deposited was actually counterfeit."In the last 24 hours, there have been two different customers who tried to pass a $100 counterfeit bill, then a little kid comes in here and asks me, 'give me ones for the $20's?' They were all fake bills," he said.In a statement, Al Feaster of the Secret Service in Philadelphia tells Action News, "Counterfeit is very widespread and it's keeping us busy...we are currently investigating a number of these cases."Officials said the counterfeiters of those bogus bills have figured out how to avoid detection by marker pens that show whether a bill is real or fake."If somebody bleaches a dollar bill and they print $20 on top of that, that pen is not going to detect anything," Emmanuel said.The Secret Service did point to a site called ''Know Your Money' to give people information on how to tell the real currency from the fake.Meantime, Vincent Emmanuel wants to warn other merchants."We want to make sure that other stores don't get burned and the people who do this kind of stuff, they should be put on notice," he said.The Secret Service estimates that roughly $45,000 to $50,000 of counterfeit money is passed weekly through the Philadelphia region.Officials advise that if there is any question as to whether the currency you have is genuine, contact a bank or local secret service office.------