A task force has been set up in the City of Industry. In the past year, it has recovered about $6.5 million worth of items, such as milk crates and pallets.
Detectives said the products are usually left behind stores and are a prime target for suspects.
"Once they collect it, they take it to sites where it's ground, palletized. This plastic grind is then sold to plastic manufacturers," said Sgt. Nabeel Mitry with the LASD.
The task force has arrested at least 50 suspects in the past year. It has also located about 20 locations used to stow or grind the stolen plastic.