An investigation has been launched after a blaze ripped through several stores in Capalaba, south of Brisbane, causing extensive damage.

Emergency services responded to the blaze about 4am this morning on Old Cleveland Road with the affected areas declared a crime scene.

An investigation will be launched into the cause of the fire, which caused extensive damage.

It was initially suspected the fire started in the Chemist Warehouse at the complex, which stretched around 50 metres long.