Authorities in Russia's Siberian region of Tuva on Monday were examining several pieces of the Progress cargo spaceship found after it crashed last week having failed to reach orbit.

Two pieces, including a large spherical object, were found by herders over the weekend, while another was discovered in the courtyard of a residential house on Monday, said the region's head Sholban Karaa-ool, warning people not to touch any metal debris.

Regional sanitation officials "inspected the spot where two pieces of the spacecraft were found in the Ulug-Khem district, on the side of the mountain and near a yurt," Kara-ool said on his official website.

"Another small piece was found in the yard of a house in the Eilig-Khem village," he said.

The regional leader added that "no dangerous substances were found" but advised people against touching the debris.

"Compatriots, if you find metal objects, don't touch them," he said.

Geochemist Tatyana Koroleva, who heads the environmental safety laboratory at Moscow State University and studied previous crashes of Proton rockets, said there is no danger from the fallen debris as any chemicals would have burned out in the atmosphere.

The reasons authorities warn people to stay away is to keep them from selling the parts as scrap metal.

"That's happened before," she told AFP.

The unmanned cargo ship Progress MS-04 launched Thursday with over 2.5 tonnes of food, water and equipment for the International Space Station, but ground control in Russia's Roscosmos space agency lost control several minutes into the flight.

The agency is currently investigating the reasons behind the crash, which could have been caused by an engine failure on the third-stage rocket, according to sources in the industry cited by Russian media.

Tuva is a mostly Buddhist region in southern Siberia and is one of the poorest parts of Russia.