Boat explosion on Hawkesbury River leaves eight people injured, two critically

Eight people have been injured, including four critically, after a boat exploded on the Hawkesbury River in Sydney's north.

Four people were taken to Royal North Shore Hospital in a critical condition, while two others were taken to Westmead Hospital in a serious condition. Two did not require transportation.

An onlooker said they were eating ice creams at the marina when they noticed the mother and toddler taking pictures near the bow of the vessel.

'Thankfully the couple with the baby were on the bow of the boat and not near the explosion, ' the witness said.

NSW Ambulance said 12 crews were dispatched to the scene along with a specialist medical team, a Toll Ambulance Rescue Helicopter and a Westpac Ambulance Rescue Helicopter.

"We've got some HAZMAT crews en route aswell because there will be a fuel spill associated with the boat", Fire and Rescue NSW Superintendent Luke Unsworth told NCA NewsWire just after 6pm.

Eight people were treated for burns after this boat exploded on the Hawkesbury River.

'NSW Police provided assistance in escorting these patients to various hospitals with medical teams awaiting their arrival'.

Firefighters were involved in driving ambulances in order to free up paramedics to work on the patients as they were raced to hospital.

The cause of the fire is being investigated.