About 200 people have been forced to leave shops and businesses around a service station near Wollongong because of a leaking underground gas tank.

The exclusion zone around the Unanderra Caltex was doubled to 200 metres on Thursday morning after a triple-zero call was made about the LPG leak about 7.40am.

Police have closed the Princes Highway in both directions and firefighters are monitoring a nearby train station, although trains are still running.

NSW Fire & Rescue Superintendent Josh Turner said the station and several other large buildings of concern were outside the exclusion zone.

“A school and a nursing home located outside the exclusion zone are being monitored but are not facing any risk under the current weather conditions,” he told AAP.

Technicians have excavated into the pit of the 17,000-litre tank to find the source of the leak.

Extracted from Prime 7.