The German public prosecution department is looking into the cases of four Dutch nationals and one Belgian at an alternative cancer treatment clinic in Bracht, Germany, officials said at a press conference on Friday.

The Telegraaf reported earlier that up to 70 patients could be involved, most of whom where Dutch.

In addition, no bodies will be exhumed as part of the investigation, officials said. Forensic pathologies have said it will be difficult to say if the patients died because of the treatment they were given or the cancer, broadcaster NOS reported.

Three of the five patients being studied have died and the two others are ‘gravely ill’, the public prosecutor said at a news conference.

Treatment

The centre, which opened in 2014, primarily treated Dutch cancer patients, most of whom had run out of options in the regular heathcare system.

The patients died in August after being given a drug thought to be 3PB, an untested medicine which is being developed at Johns Hopkins University in Baltimore, according to website Science.

The clinic’s founder Klaus Ross may have given the patients an overdose of the drug after switching from a prepared dose of the drug to a powder which he mixed himself, NOS said.