*Updated 3:41 p.m.
The detonated package contained a brick of marijuana, the Tribune reports. The sergeant estimated it to be more than a pound.
The package did not contain an explosive and normal activity at the mall has resumed, according to Arcadia Patch.
Police set up a perimeter around the package and the bomb squad has detonated it, Arcadia police Sgt. Dan Crowther told San Gabriel Valley Tribune. The package's contents remain under investigation.
Arcadia Police has not evacuated the mall, Arcadia Patch reports.
12/20/2012 at 11:45 a.m.
The Los Angeles County Sheriff's Department bomb squad is investigating a suspicious package found in the parking lot of the Westfield Santa Anita Mall on Thursday morning, Arcadia Patch reports.
Arcadia Police called the bomb squad when they could not identify the package, police spokeswoman Patty Barragan told Arcadia Patch. The package is still under investigation as of Thursday at 11:45 a.m.