PHILADELPHIA – Convenience store employees are now eyeing customers with hot drinks more carefully after a string of robberies involving throwing scalding liquid on cashiers before grabbing money from the register.

Within the past week, up to16 such occurrences have happened throughout Delaware County since last Thursday, four attacks have surfaced in Delaware and Philadelphia, the Delaware County Times reports. The thieves, working in pairs, with one grabbing a cup of hot coffee and throwing the liquid at the cashier, while the other empties the register. The thieves have targeted local Wawa and 7-Eleven convenience stores, and both companies are offering separate $5,000 rewards for information leading to an arrest.

NACS offers tips on how to make locations undesirable to robbers and safer for employees and customers. NACS spokesman Jeff Lenard told the newspaper that cash management is key to reducing the likelihood of an incident. "If (robbers) know the money isn’t there, they’ll be less likely to target your store," he told the newspaper. He added that criminals do "case the joint," and if they see proper cash management in place, they are less likely to target a store.

Lenard recommended that stores with signage that emphasizes they do not keep much cash in their register drawers to actively continue that practice.

Another way to reduce robberies is high visibility. Make it equally possible to see inside the store and outside the store by reducing signage in the windows, Lenard said.

Also, security experts stress a policy of non-resistance when facing robbers, Lenard noted.