A woman got more than she bargained for when she opened what she thought was the yoga mat she had ordered from Walmart. Instead, she came across in the box around 20,000 oxycodone pills worth $400,000 (£302,000).

The woman in South Carolina who did not want to be identified told WSOC-TV that there were so many pills in the box that they were spilling from the packaging. She quickly called police.

Officers who responded found two large silver aluminum-type packs that had been ripped open containing the pills, which were stamped with an A/125 imprint.

The drugs were shipped from Newport Beach, California to the woman's old condominium in Rock Hill, South Carolina, police said.

York County Miltijurisdictional Drug Enforcement Unit commander Marvin Brown told WSOC-TV that drugs are often delivered to empty homes where someone is waiting for them to arrive.

"Vacant apartments, homes where people have gone to work for the day," Brown explained.

In this case, however, a misspelled street name on the package prompted the post office to look up the woman's address and forward it to her new home. "The dealers weren't as intelligent as they thought they were," Brown said.

Police seized the pills, which are believed to be counterfeit oxycodone from Mexico. Authorities are working to trace the package to see where it was headed and who was supposed to get it.