Journalists in northern Russia say they have measured high levels of radiation near two abandoned barges, which were reportedly brought ashore after last month’s mysterious explosion at an Arkhangelsk region military testing range.

The blast, which has been the focus of international speculation, killed five nuclear scientists and caused radiation levels to spike briefly in nearby Severodvinsk by as much as 16 times normal levels.

Russian officials have released only sketchy information about the accident, saying that the weapons test gone wrong involved “isotopic sources of fuel on a liquid propulsion unit.” US news outlets, citing intelligence sources, have reported the blast occurred during a mission to salvage a nuclear powered cruise missile from the bottom of the White Sea, off Russia’s Arctic coast.

President Vladimir Putin confirmed late last month that the blast resulted from a test of a promising new weapon, though he failed to explain the radiation blips.

Exactly what kind of nuclear device was involved in the explosion remains unclear. According to data from Rosgidromet, Russia’s federal weather agency, the blast released a bouquet of radioactive isotopes that experts say could only have come from a nuclear reactor accident.

Descriptions from Rosatom, Russia’s nuclear Corporation, suggest a different sort of device from a reactor. In one statement to the Russian media, the corporation called it a “nuclear battery.”

On Monday, journalists in the Arkhangelsk region reported that the two barges had turned up on a local beach, where they have laid for the weeks since the apparent missile accident, emitting radioactivity.

Radiation measurements as high as eight times normal background levels were taken on August 31 from a distance of 150 meters, while earlier tests soon after the barges arrived peaked as high as 38 times normal, the reporters said in a video released on local television. Those levels are still well short of life threatening, but measurements closer to the barges haven’t been made.

The floating platforms could provide more clues as to what happened, but for now they only deepen the mystery. Both  contain partially destroyed industrial equipment and have remained on the shore unguarded and without any explanation from authorities.

A still from a video taken by reporters from the Belomorkanal TV program of the irradiated barges. Credit: Youtube still/Belomorkanal TV

One was towed there on August 9, the day after the blast. The other arrived five days after, according to villagers who were quoted by the Radio Free Europe/Radio Liberty news agency.

What remains unknown is why – or, indeed, if ­– Russian authorities would have abandoned radioactive debris from a high-profile accident, which has fueled speculation abroad and radiation fears at home.

The Soviet Navy had a long history of abandoning nuclear waste, nuclear reactors, and even entire nuclear submarines, at sea. The scale of these irradiated dumps was finally made public in 1994, when the newly formed Russian government admitted to the practice and promised to stop it.

On Tuesday, Rosatom would not comment on the discovery of the platforms, telling RFE/RL that the corporation “is not in a position to comment on classified defense contracts and military tests.”

One of the platforms, reported RFE/RL, supports a damaged crane and a ladder for scuba divers, along with what appears to be a container for radioactive materials. This would lend credence to US intelligence reports of an underwater mission to recover a nuclear powered missile.

The presence of the platfroms, said the agency, also matches up with satellite images taken of the White Sea accident in its immediate aftermath.

Radiation readings taken by the journalists on Saturday, August 31 measured from 70 to 186 microroentgen per hour. Earlier measurements in August peaked at 750 microroentgen per hour. Normal local background levels in the area are closer to 20 microroentgen per hour, Vice News quoted Greenpeace as saying.

“This beach should be decontaminated,” Bruno Chareyron, a research director at the French radiation-monitoring NGO CRIIRAD, told RFE/RL.

“The authorities should collect the radioactive debris [and] monitor the contamination of the water, sand sediments, fauna and flora,” Chareyron was quoted as saying.