Suspicious fire at Sydney factory

A suspicious fire has damaged a Sydney factory that might have housed a clandestine drug laboratory, police say.

Firefighters contained the blaze to the second floor of the building on Underwood Avenue in Botany just after 7pm on Wednesday, a Fire and Rescue NSW spokeswoman told AAP.

HAZMAT crews were also called to the site, where police have set up a crime scene to investigate the cause of the blaze.