State prosecutors said Thursday that the crackdown involving prosecutors, police and government officials would continue until the end of October.
The move came after the Korea Food and Drug Administration (news - web sites) (KFDA) said at least 19 firms had produced what newspapers called "garbage" dumplings by using imported radish from China that was unfit for human consumption.
Dumplings, prepared by stuffing seasoned minced meat and vegetables inside a flour-based "skin," are popular in South Korea, China, Japan and elsewhere in Asia.
"The companies were found to have used harmful radish for their dumpling products," said KFDA chief Shim Chang-Koo.
"Tigher regulations are needed to punish food-related crimes," he added.
The dumpling scandal flared on Monday, triggering a public outcry. Civic groups have demanded tighter food quality control and harsh punishment for violators.
The government and the ruling Uri Party agreed Wednesday to push for a revision of South Korea's food hygiene law to strengthen the punishment of manufacturers of unsafe foods.
On Tuesday, Japan's health ministry stopped processing dumpling imports from South Korea, effectively banning their entry into Japan.
Japan imported 864 tons of frozen dumplings from South Korea last year. This year so far, Japan has imported 437 tons of frozen South Korean dumplings, according to the ministry.
"We are waiting for South Korea to officially tell us about the situation and which companies are involved in the scandal," said an official with the health ministry.
"Once we know which firms are involved, we can take the next step" of banning dumpling from certain firms and of recalling the ones that already were shipped to stores.