Early Friday morning, emergency services were called to fight a fire at Ladle of Love Cafe in Little Sturt Street.
Fire fighters and police arrived just before 5am and contained the fire.
A gas pipe at the rear of the building appears to be the cause. Initial investigations suggest the pipe shows signs of tampering.
No one was injured in the blaze. The extent of the damage is unclear at this time.
Police are urging anyone who saw suspicious activity or have further information to contact Crime Stoppers on 1800 333 000 or report online at crimestopperssa.com.au