A fleet of Earth-monitoring satellites has joined the search for missing Malaysia Airlines flight MH370, the organisers of the satellite pool said on Wednesday.
China on Tuesday requested activation of the so-called International Charter on Space and Major Disasters, the organisation said on its website.
Under the agreement, 15 space agencies or national space institutes help emergency or relief efforts by passing on images from satellites flying over the location.
"Satellite imagery is now being employed to search for any evidence of the plane, both before and after it disappeared," the website said.
"As of 12 March 2014, the search remains ongoing."
The activation request came from the China Meteorological Administration, it said.
"They are providing high-resolution data," a European Space Agency (ESA) official, whose organisation is a charter member, told AFP.
He was unable to say which geographical areas were being covered.
The Charter, which took effect in 2000, has been activated more than 400 times, but this is the first time it has been called in to help the search for a missing aircraft, according to records of its operations.
It has been mostly used in the aftermath of earthquakes and floods when rescue teams needed to identify badly damaged zones or roads, railways and bridges that are still passable.
It was invoked last November to aid swathes of the Philippines ravaged by Typhoon Haiyan.
Its biggest operation was three years ago, following the earthquake and tsunami that struck northeastern Japan, when a hundred maps were drawn up from its data.
Once activated, space technicians determine which satellites are available and best suited for the task of providing ground radar data or photos.
They then send a request to the satellite's operator, which programmes the orbiter to take pictures as it flies a zone. The data are usually available within 24 hours and are provided for free.
US satellite firm DigitalGlobe has set up a crowdsourcing platform, inviting Internet users to comb through images to search for clues of the missing aircraft.