The latest robbery happened Thursday night at an indoor swap meet on Paramount Boulevard in Pico Rivera.
Investigators say a group of robbers struck at about 6:15 p.m., smashing open display cases and grabbing jewelry valued at a total of $15,000.
Police described the suspects as black men, between 20 and 25 years old, wearing black clothing and hooded sweat shirts.
Suspects arrested in earlier thefts are all members of the same Los Angeles gang.
