An eyewitness has described hearing a big bang as a boat went up in flames on Lake Taupō this afternoon.

Police were alerted to a medium size boat fire at Kincloch in Lake Taupō about 2.50pm. The boat was engulfed.

Boat fire on Lake Taupo off Kinloch Beach. Photo / Supplied

New Zealand Fire service shift manager Colin Underdown said all passengers were accounted for although the number of passengers was unknown.

The fire service was at the lake liaising with the Harbour Master and Coastguard. The boat was still drifting, he said.

Earlier a police spokesperson said several other vessels had gone to help the boat and confirmed all on board were safe and well.

Brittany Rose was enjoying a day with family in Kinloch at Lake Taupo when they heard a big bang as the boat went up in flames.

Rose said she screamed for people to go help and said a man ran to his jet ski and “blasted” out to the boat.

The boat before it burst into flames. Photo / Brittany Rose

Rose believed no one was hurt in the incident.

After the bang, Rose said the boat started to smoke before going up in flames.

She said people were able to get out to the boat to help before it went up in flames.

More to come.