A state investigation was unable to find what caused an E. coli infection that led to the death of a 3-year-old Wright County girl and seriously sickened her 5-year-old brother.

“Unfortunately, we were not able to identify the source of the children’s infections,” said state public health veterinarian Joni Scheftel of the Minnesota Health Department.

The children, Kade and Kallan Maresh, were sickened on July 9 with E. coli infections that led to a serious form of kidney failure known as hemolytic uremic syndrome. Kallan Maresh died one week later in the hospital. Kade Maresh has since been released from the hospital and is recovering.

Although the children had visited a petting zoo, which can be a potential source of E. coli contamination, health officials ruled it out after tests.

“In particular, we did not find a connection with a petting zoo that the children visited, despite extensive testing of the animals,” said Scheftel.

Investigators also looked at foods the children ate, such as ground beef, leafy greens and raw milk, swimming locations, person-to-person transmission in families or day care, and other farm animal contact.

Scheftel said there have been no other reported cases of infection with the same strain of E. coli and that monitoring will continue to look for other cases that may lead to the source of the infection.