OSAKA--Japan's current bubble tea craze has sent tapioca imports soaring to meet the demand for the drink made with cold milk and tapioca balls.

Osaka Customs on Aug. 19 said that between January and June, 4,471 tons of tapioca were imported to Japan’s five regions, including the Tokyo and Osaka metropolitan areas, 4.3 times more than the 1,038 tons in the same period last year.

The Osaka metropolitan area, which includes Kobe and Kyoto, saw the largest growth in tapioca imports. They ballooned to 633 tons, 21 times larger than 30 tons recorded in the first half of last year.

Japan imports tapioca, which is made of cassava starch, mainly from Taiwan, where the drinks are also hugely popular.

Tapioca booms have hit Japan before. This latest one, which started brewing a few years ago, began in the Tokyo metropolitan area.

The success of bubble tea there inspired shops in Osaka and Kobe to start selling tapioca products, so imports via Kobe Port and Kansai Airport started to soar, said an Osaka Customs representative.

Restaurants offering tapioca beverages and food items soon popped up in central Osaka and convenience stores and supermarkets started selling them.

A conveyor belt sushi restaurant chain headquartered in Osaka added them to the menu this year.

Osaka's increased interest in all things tapioca pushed imports to the Osaka metropolitan area between January and April beyond those for all of 2018.