SIOUX FALLS, S.D. (KELO) — Sioux Falls police are investigating two private sales over the weekend involving fake cash and fake phones.

One case involved the sale of jewelry where the buyer paid with fake money. In the second case, the victim thought they were meeting to buys some cell phones but the devices ended up being for demo use only.

“These private sales, take that with a grain of salt. If it seems too good to be true, it may be too good to be true. There are people looking to take advantage of others sometimes we’ve had thefts and robberies that have happened from this,” Sioux Falls Police Public Information Officer Sam Clemens said.

Police encourage people engaging in private transactions to utilize the “Safe Exchange Zones” at the Law Enforcement center in downtown. There are security cameras in the lobby and the parking lot.