Two people have been treated by paramedics and an international mail centre in Sydney’s west has been evacuated after a small amount of a corrosive solvent was spilt in a mail-sorting area.

About 150 workers were moved from Australia Post’s international mail centre at Granville, seven people were assessed by paramedics, and two were treated after the spill on Wednesday afternoon, Fire and Rescue NSW Superintendent Ian Krimmer said.

A 40-year-old woman was treated for respiratory problems, the Nine Network reported.

Twenty firefighters are at the scene.

“We’re just in the process of using sand to soak up the spillage,” Supt Krimmer said.

Authorities are “yet to fully identify the nature of the substance”, he added.