UPDATED at 11:15 a.m. with ages of suspects and new details on the incident.

SOUTH ST. LOUIS COUNTY • A customer cooking a so-called "one pot" batch of methamphetamine inside a pop bottle in her purse caused the Thursday night evacuation of the South County Walmart store.

The woman, 32, was caught shoplifting an item unrelated to meth-making when store security and then police discovered the 20-ounce bottle, St. Louis County police Lt. Mark Cox said. The store full of customers at Telegraph Road and Interstate 255 was evacuated about 6:15 p.m. because of the possible dangers of the chemical concoction.

"It had the potential to be flammable or blow up at any time," Cox said. He described the initial situation inside the store as "volatile," but said the evacuation was mostly precautionary.

Police said Walmart staff confronted the woman outside the store after she walked out with cosmetics and a purse. Police said she hadn't paid for the items. She was brought back to an office where employees found the bottle in her own purse.

No one was injured. Aside from the bottle, no harmful substances or fumes were discovered inside the store.