A woman shot pepper spray to keep shoppers from merchandise she wanted during a Black Friday sale, and 20 people suffered minor injuries, authorities said.

The incident occurred shortly after 10:20 p.m. Thursday in a crowded Los Angeles-area Walmart as shoppers hungry for deals were let inside the store.

Police said the suspect shot the pepper spray when the coverings over the items she wanted were removed.

"Somehow she was trying to use it to gain an upper hand," police Lt. Abel Parga told The Associated Press early Friday.

He said she was apparently after some electronics and used the pepper spray to keep other shoppers at bay.

Officials said 20 people suffered minor injuries. Fire department spokesman Shawn Lenske said the injuries to least 10 of them were due to " rapid crowd movement."

Parga said police were still looking for the woman.

The store remained open and those not affected by the pepper spray continued shopping.