One of six people suspected of contracting hepatitis E after eating pork intestines at a barbecue restaurant in Kitami, Hokkaido, has died, health ministry and Hokkaido government officials said Sunday.

The hepatitis E virus is easily destroyed by heat, and infection through food can be prevented if meat is cooked at a sufficiently high temperature.

Patrons at the restaurant grill their own meat and officials suspect the intestines were not sufficiently cooked. Hokkaido government officials are investigating how the six contracted the virus.

There have been cases in which humans have been infected with the virus after eating fresh wild deer or boar meat. However, officials say they believe it is the first time an infection has been confirmed among people who have consumed meat cooked at restaurants or at home which has gone through proper distribution channels.

According to the ministry and Hokkaido government officials, the six people -- all relatives -- ate at the restaurant in mid-August. A man in his 60s developed fulminant hepatitis in late September and died the following month. A blood test showed he had hepatitis E.

A followup investigation by the Hokkaido government found the virus in the blood of one of the deceased man's sons and in the blood of four others in the group. Antibodies, which indicate the presence of the virus, were also detected.

The son donated blood in September and a man who received a transfusion of his blood has also been found infected with the virus, according to health officials.

The Hokkaido government is checking on the health of others who ate at the same restaurant.

Most young pigs contract the virus but it is believed to be eliminated almost entirely before they are shipped for human consumption. But the virus is said to survive sometimes in the pigs' internal organs such as the liver.

There has been an unconfirmed report of the virus having been detected in pork liver put on the retail market in Hokkaido.