7Up—the lemon-lime soda sometimes thought to be named for its original seven main ingredients—now has a troubling eighth ingredient in Mexico: methamphetamine.

Health professionals in Arizona are warning travelers to the Mexicali area to be aware of possibly contaminated sodas there. The warning comes days after medical toxicologists and emergency doctors received reports of soda tampering in the area.

According to the Attorney General of the State of Baja California, seven people were sickened and one died from the spiked soft drinks. Officials requested that merchants there suspend sales of 7Up and clear the product from their shelves. And an investigation is now in progress to figure out how the illicit stimulant got into the soda.

Chris Barnes, a spokesperson for Dr Pepper Snapple Group, told Arizona news outlet AZCentral that 7Up products in the US were safe. “None of the 7Up products sold in the US are affected by the issue being reported in Mexico,” Barnes said. “Dr Pepper Snapple owns and licenses the 7Up brand only in the US and its territories. We do not market, sell, or distribute the brand internationally.”

Health professionals recommended travelers stay watchful of the beverages they buy. “It is important to check that the seal for any food and drink consumed is still intact and show no signs of tampering,” Dr. Daniel Brooks, a poison and drug expert with Banner Health, said in a statement. “If you notice any difference in color, taste, or smell, throw it out.”

Symptoms of consuming meth-laced soda include: burning to the esophagus or abdomen, nausea, vomiting, difficulty breathing, and fast or irregular heartbeat.

This is not the first time 7Up has contained a potent drug. When the soda was first released in the 1920s, it contained lithium citrate, a mood-stabilizing psychiatric drug that’s used to treat manic states in people with bipolar disorder. Some have theorized that the soda got its name from the atomic mass of lithium, which is roughly seven.