Feb. 10 -- Refined-tin shipments from Indonesia, the world’s largest exporter, plunged 64 percent in January from a month earlier after bad weather disrupted mining, reducing ore supplies to smelters.

Exports dropped to 5,380 metric tons from 15,103 tons in December, Toto Rusbianto, head of mining exports at the Trade Ministry, said in a mobile-phone text message today. Sales were 7,335 tons in January last year.

Lower sales from Indonesia may help to sustain a 30 percent rally in prices this year spurred by concern that demand for the metal used in soldering and packaging will outstrip global supplies. Tin inventories monitored by the London Metal Exchange fell to the lowest level since March 2009 yesterday.

“Extreme weather has really disrupted both offshore and on-land tin mining in Bangka,” Johan Murod, director at PT Bangka Belitung Timah Sejahtera, a group of six smelters, said by telephone from Pangkalpinang. “Waves could reach as high as 5 meters, making it impossible for dredgers to operate, and on land the pits were flooded due to heavy rain.”

Shipments also fell last month as producers had limited stockpiles after boosting sales in December, Murod said. Smelters in Indonesia ended a voluntary ban on shipments on Dec. 31, clearing the way for exports to resume. The ban was intended to boost prices after a slump in August and September.

The weather conditions may persist until next month or April, and exports this month may reach only about 4,000 tons, Murod said. The Bangka Belitung islands are Indonesia’s main producing regions.

Indonesia shipped tin to 11 countries last month, with Singapore taking 3,560 tons, or 66 percent of the total, the ministry’s data showed.

Three-month delivery tin fell 1.6 percent to $25,000 a ton in London at 11:05 a.m. Jakarta time.