It was reported that debris had been seen in the lake, around 150m offshore from Breaksea Bay, police said.
The Westpac Rescue helicopter had searched this afternoon for signs of the helicopter and its pilot.
Police search and rescue personnel were this afternoon en route to the location, which is in a remote bush area, accessible only by four-wheel drive.
Police were to remain at the scene overnight and a full ground and water search would begin at first light tomorrow.
The Hughes 500 is one of the most popular light-turbine choppers in the world.
New Zealanders James Innes, 59, and his son Andrew, 30, died in July 2008 when their Hughes 500D crashed minutes after taking off from the Carbon County Airport in Utah in the United States. A third man, George McDaniel, 40, from Idaho Falls, also died.
Ten years prior, James Innes's eldest son, Dan, and two New Zealanders were killed when their Hughes 500 crashed while they were rounding up sheep on Tiburon Island in the northwestern Gulf of California.
In 2006, Taupo pilot Bruce Lilburn and his four passengers were injured when the Hughes 500 they were in crash-landed on Mt Ruapehu's crater lake.