CHICAGO (CBS) -- The FBI is asking for help from the public in finding a man they say used Snapchat to lure at least four minors into producing sexually explicit videos and images.

Michael Ramos, 46, is charged with four counts of production of child pornography, and one count of possession of an electronic device containing child pornography.

Investigators are concerned there may be more victims.

The FBI said Ramos went by more than a dozen screen names on Snapchat. They included:

• michaelramos197
• myislandmylove
• damikey
• damikey77
• lizziedu49
• young-goddess1
• tony2tooth
• jhonnybreal
• fukuall007
• damikey007
• crystal_ebk
• l05tsoul

Anyone who believes they or someone they know may have been victimized by Ramos should contact the FBI at (800) CALL-FBI, or by email at MichaelRamosVictims@FBI.gov.