In two separate incidents last week, the suspects approached business owners who did not have fair labor standards signs posted and demanded $200 for the sign, according to police.
The suspects threatened to fine the merchants $3,000 if they did not comply, police said.
The incidents happened Thursday in the 3300 block of 23rd Street and Friday in the 3200 block of 22nd Street.
One merchant made out a $200 check to the suspects but later stopped payment, police said.
The other told the suspects she did not have the money but would pay them the next day if they came back, which they did not, police said.
Any business owners approached in similar scams are advised to call police.
Fair labor standards posters are available at no cost to businesses by calling (415) 703-4810 or by visiting www.dir.ca.gov.