Assistant Chief Rick Flanagan said the suspects burglarized the restaurant early Monday, then started the fire with a blowtorch to cover their tracks. Police said all four confessed to the crime.
The suspects were identified as Pedro Israel Loredo, 19; Juan Manuel Torres, 17; and Allen Gerome Davis, 17. A 15-year-old boy who worked at the restaurant also was arrested.
Prosecutors had not filed charges by late morning.
The blaze killed firefighters Lewis Mayo, 44, and Kimberly Smith, 30, who were trapped beneath a roof that collapsed while they were battling the flames.
Smith was the first female firefighter in Houston to die in the line of duty.
"When a member loses his or her life to an accidental fire we understand that, but it still hurts," said Robert Parry, spokesman for the local firefighters' union. "But when it's an arson fire, intentionally set - just plain murder - our broken hearts break even more."