BOSTON -- More than half of paper money collected in the southeastern part of the state tested positive for cocaine, according to a study conducted by a professor at the University of Massachusetts at Dartmouth.

Chemistry professor Yuegang Zuo said he found traces of the drug on 67 percent of paper bills collected from area supermarkets during the past two years.

The study found higher residue amounts of cocaine on higher denomination bills -- especially 10s, 20s and 50s.

Previous studies have also found a large percentage of currency contaminated with cocaine.

In the 1990s, a Drug Enforcement Agency study found that about a third of currency samples taken from Chicago banks and the Federal Reserve Bank of Chicago contained traces of cocaine. In another study, out of more than 135 bills collected from restaurants, stores and banks in seven cities, all but four bills were contaminated, the Standard Times reported.