Four men were rescued after their barge capsized off the Sydney coast yesterday. 

The incident happened off Great Mackerel Beach at about 1pm, when the barge, which was carrying a sewage truck, overturned, sending three members of the crew overboard. 

One of the men was temporarily trapped under the barge before being freed, according to reports.

NSW Ambulance Special Operations Team Craig Anson said: "On arrival, we found the occupants from the barge had managed to safely make their way away from the barge to a nearby boat." 

The men were treated for minor injuries at the scene. One man was later taken to Northern Beaches Hospital in a stable condition. 

A clean-up operation is under way and is expected to take up to three days to complete, after authorities placed a boom around the barge to contain the spill.