A group of researchers from the University of Alberta and China’s Huazhong Agricultural University found that cooking ground beef at the 160-degree F (71 degrees C) temperature recommended by government officials in the U.S. and Canada may not be hot enough to kill all the strains of Escherichia coli (E. coli), according to a research article.

E. coli, a bacteria that’s found in the gut of both animals and humans, is not always harmful. However, some strains, such as O157, can cause kidney failure or even death, according to a news release from the University of Alberta.

According to the research article, the scientists discovered 16 genes in fresh meat that are extremely heat-resistant. These genes make up about 2% of the entire E. coli strains.

Lynn McMullen and Michael Gänzle, food microbiologists at the University of Alberta, along with several graduate students, led the E. coli research. According to the statement from the University, they first became aware of the inconsistent behavior of E. coli eight years ago.

In 2008, McMullen and Gänzle asked a student to look at the differences amongst organisms in a batch of E. coli from ground beef. Elena Dlusskaya, the student who conducted the experiment, found that one organism survived in the beef despite being in 140 degree F heat. The results were odd, considering most E.coli is killed in a matter of seconds after a certain temperature is applied. McMullen and her colleagues decided to investigate.

“These organisms aren’t supposed to survive, but every once in a while they do,” said McMullen in the press release from the University of Alberta. “So we decided to find out why. We looked at the genomes to see what was different.”

Now, the team is researching how problematic the occasional survival is across strains of E. coli. The findings call the temperature recommendation of cooking ground beef to a minimum of 160 degrees F (71 degrees C) into question as well as suggesting heat resistance could be the reason for sporadic cases of E. coli.