Firefighters fear factory blaze will continue for at least one more day

Fire crews are still working to extinguish a huge factory fire in western Sydney that burned fiercely through the night.

Streets were shut down around the factory site at Church Road in Moorebank after it exploded into flames around 6.30pm yesterday.

The extended road closures, which prompted lengthy traffic delays during this morning's peak, were lifted by midday today.

When fire crews arrived at the scene last night, they found a large amount of cardboard burning at the rear of the building, believed to be owned by a healthcare company.

The blaze quickly spread throughout the factory and at one point flames jumped to 10 metres in height.

Flames and plumes of smoke were seen by motorists travelling on the M5.

Workers from the factory and neighbouring buildings were evacuated and surrounding streets closed off as spot fires spread in nearby Clinches Pond Reserve.

Firefighters remain concerned it could continue burning for several days.

There are no reports of injuries.

"This fire will burn for the next 24 hours or maybe longer. It is a significant fire and will impact the local area," a NSW Fire and Rescue spokesman told 9News earlier today.

Fire investigators is beginning their inquiries into the cause of the blaze.