Story highlights A boat turns up a sonar signal that looked like it's coming from a man-made object

MH370 searchers use high-resolution sonar to make a picture

Experts say the discovery is probably a shipwreck from the early 1800s

(CNN) For nearly two years, boats dragging high-tech detection devices across the Indian Ocean have failed to solve the mystery of the whereabouts of Malaysia Airlines Flight 370.

But in December one boat raked up a different one -- a shipwreck some 200 years old at the bottom of the sea.

"An anomalous sonar contact was identified in the course of the underwater search, with analysis suggesting the object was likely to be man-made, probably a shipwreck," said the Joint Agency Coordination Centre, the Australian agency directing the search for MH370, the Boeing 777 that mysteriously disappeared in March 2014 en route from Kuala Lumpur, Malaysia, to Beijing.

Technicians work on an autonomous underwater vehicle in 2014.

Searchers sent out a second boat, Havila Harmony, this month to take a picture using the sonar on board an autonomous underwater vehicle, the agency said in its latest operational report.

They showed the image to experts at the Shipwreck Galleries of the Western Australian Museum who said the wreckage is probably a ship made of steel or iron from the early 19th century.

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