A deadly and highly contagious pig virus continues to spread across Ontario as officials confirm a fourth case of the outbreak has been found in the province.

Officials say two new cases of porcine epidemic diarrhea have been confirmed through laboratory tests.

One case -- a farm in Chatham-Kent -- was flagged earlier this week as under investigation after pigs there fell ill.

A spokeswoman for the province's Ministry of Agriculture says the latest case was found at a farm in Norfolk County, which is on the north shore of Lake Erie.

Susan Murray says authorities expect to find more cases since PED is so easy to transmit.

A group representing the province's hog farmers has said the virus is spread through contact with manure, which can cling to trucks, trailers and even clothing and boots.