An asteroid twice the size of the one that blew up over Russia three years ago is likely to have whipped past the earth early this morning.
The asteroid came closer than some of the communications satellites that orbit the planet.
Otago Museum director Ian Griffin said the asteroid had been difficult for astronomers to track, but it was likely to have passed earth about 3am New Zealand time.
"Some of them are in tricky orbits and you can't see them very easily," Dr Griffin said.
"And this one has been basically too close to the sun for the last few months for astronomers to see it and that's the reason it's been a bit uncertain about exactly how far away it passed us."
He said the asteroid could pass the Earth again in a year's time, but it would not hit the planet for at least another 100 years.
The meteorite that exploded over central Russia in February 2013 sent fireballs crashing to earth and injured 1200 people as its shockwave shattered windows and damaged buildings across a wide area.
The main damage was in the city of Chelyabinsk, home to a nuclear power plant and the Mayak atomic waste storage and treatment centre as well as many factories, about 1500km east of Moscow.
Thought to weigh 10 tonnes and travelling at 30km per second, the meteor partially burned up in the earth's lower atmosphere, sending blazing fragments across the sky and causing damage in six cities.
Russia's Academy of Sciences said the meteor entered Earth's atmosphere and broke apart 30 to 50km above ground.
The energy released when it entered the Earth's atmosphere was equivalent to a few kilotonnes, the academy said - the power of a small atomic weapon exploding.