Arkansas ? Tests of two Chinese brands of dog treats sold at Wal-Mart stores found traces of melamine, a chemical agent that led to another massive pet food recall in March, a spokeswoman said Tuesday.

Wal-Mart Stores Inc. quietly stopped selling Chicken Jerky Strips from Import-Pingyang Pet Product Co. and Chicken Jerky from Shanghai Bestro Trading in July, after customers said the products sickened their pets.

No recall was announced at that time, but Wal-Mart said in a statement Tuesday that customers who bought one of the products should return it to the nearest store for a refund.

Company spokeswoman Deisha Galberth said 17 sets of tests done on the products found melamine, a contaminant that’s a byproduct of several pesticides.

“There were very small amounts of melamine found,” Galberth told The Associated Press. “The amounts were so small the laboratory recommended more testing.”