Health authorities searched a second Kobayashi Pharmaceutical factory in western Japan on Sunday after the company reported five deaths possibly tied to dietary supplements, an official said.

The inspection in Wakayama prefecture follows one on Saturday in Osaka, expanding the investigation into the drugmaker's use of "Beni-Koji" red yeast materials.

Osaka-based Kobayashi said it found what appeared to be potentially toxic puberulic acid that could have been produced by blue mould penicillium in Beni-Koji materials produced between last April and October at the Osaka factory.

As of Friday, 114 people had been hospitalised and five had died after taking the supplements, which were marketed as helping lower cholesterol levels, the company said.

The cause of the deaths has not been confirmed, the official at Japan's Health and Welfare Ministry told Reuters. But "it is suspected that Beni-Koji may be the cause, so we have inspected two factories in two days."

Kobayashi said on Friday it was investigating a suspected link between the products and their effects on the kidney since it received reports of kidney disease linked to the products.

"We will fully cooperate with the investigation so that we can resolve the problems as early as possible," the head of Kobayashi's investor relations, Yuko Tomiyama, told reporters on Sunday in footage shown by public broadcaster NHK.

The health official said the ministry "would join hands with other ministries concerned to do our utmost to resolve the ongoing case while asking Kobayashi Pharma to cooperate as needed in looking into the case".

The factory in Osaka's Yodogawa Ward was closed in December due to ageing facilities and production shifted to the factory in the city of Kinokawa that was searched on Sunday, Japanese media reported.

The government has criticised the company for taking two months to announce the health impacts of its products. Kobayashi began recalling products on March 22 after receiving reports of kidney ailments.

Its products are also consumed in other countries.

Japanese media said a case of acute renal failure had been reported in Taiwan. Taiwan's food and drug administration is investigating three "unexpected health reactions" that may be related to imported materials from Kobayashi, Taiwan's official Central News Agency reported.

A Chinese consumers association urged consumers to stop using potentially affected products, saying it was concerned about the risk of Kobayashi products, state media reported on Friday.

Japan's health ministry is aware of the Taiwanese cases, the official said, declining to comment further on any international cases.

South Korea's ministry of food and drug safety has posted the list of 182 Japanese recalled products made by Kobayashi and other companies that contain red yeast rice, asking consumers not to purchase those items online.

The South Korean ministry said on Friday that authorities would dispose or return shipments related to the Kobayashi case at customs. It did not respond to a request for additional comment outside normal business hours.

Kobayashi sells Beni-Koji wholesale to 52 companies, which have conducted voluntary inspections and found no materials requiring medical consultation as of Friday, NHK said. Those companies sell the materials on to 173 others, it said.

TV Asahi reported that some 1,800 foodmakers could be affected.

Beni-Koji contains Monascus purpureus, a red mould used as a food colouring.