If the solar system's first confirmed interstellar visitor was an alien craft, its makers don't seem to want us to know.
Astronomers are poring over data collected by the Breakthrough Listen project, which spent six hours scanning the mysterious Oumuamua asteroid overnight (NZ time).
So far they're found no signs of any electromagnetic signals emanating from the bizarre cigar-shaped object, which appeared out of nowhere and flew by the Earth in October.
"Listen observed Oumuamua across four radio bands spanning billions of individual channels across the 1 to 12 GHz range," the Stephen Hawking-led group said in a statement.
Ninety terabytes of data was collected - enough to fill 19,000 DVDs - so it could take a while to sift through it all.
"It is great to see data pouring in from observations of this novel and interesting source," said Andrew Siemion, director of the Berkeley SETI (Search for Extra-Terrestrial Intelligence) Research Center.
"Our team is excited to see what additional observations and analyses will reveal."
Oumuamua made its dramatic entry in October, coming from above the plane the solar system's planets and asteroids sit. It swung around the sun, and is currently on its way out. It's approximately twice the distance between the Earth and the sun away already.
Earlier this week an astronomer at Penn State University said there was evidence Oumuamua isn't a natural object, suggesting it could be a self-replicating probe with failed engines.
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Breakthrough Listen has released some of the data it has collected for the public to examine - but is pessimistic about the chances of an amateur finding something they've missed.
"The data is stored in specialised formats, and analysing it may be challenging for non-experts. We invite those who are interested to study the tutorial material provided by the Breakthrough Listen science team... and to assist with the analysis not only of this intriguing object, but of the entire Breakthrough Listen dataset."
Breakthrough Listen aims to survey 1 million stars in our own galaxy, and 100 nearby galaxies for signs of extra-terrestrial life.