TOKYO, Japan - The Japanese government began a rare auction on Monday of its emergency rice stockpiles in a bid to help drive down the surging price of the national staple.

Rice shortages driven by factors from poor harvests caused by hot weather to panic-buying over a "megaquake" warning last summer have caused prices to nearly double over a year.

Exacerbating the problem, some businesses are also thought to be keeping their inventories and waiting for the most opportune time to sell.

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Japan stores about a million tons of rice for emergencies.

The country has previously tapped into these reserves during disasters, but this is the first time since the stockpile was built in 1995 that supply chain problems are behind the move.

The agriculture ministry is expected to select successful bidders for 150,000 tons of rice by Wednesday -- with the auctioned grain expected to hit store shelves by the end of March.

The ministry says it plans to release another 60,000 tons if necessary.

"This is a highly irregular situation," agriculture minister Taku Eto told parliament on Monday.

"By sorting out the clogged parts of the distribution network, we hope to relieve the hardship experienced by consumers."

Experts say several factors have contributed to the crisis.

Among them is a tourism boom and shortages caused by record heatwaves in recent years, as Japan, like other countries, experiences the effects of human-driven climate change.

In August last year, shelves in some stores emptied after the government warned of a possible "megaquake", along with one of the fiercest typhoons in decades and the annual Obon holiday.

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© Agence France-Presse