Nearly all the deaths being investigated at a German alternative cancer clinic involved Dutch patients, the Telegraaf said on Friday.

In total, 70 suspicious deaths are being looked into at the clinic, run by therapist Klaus Ross, which hit the headlines earlier this month after several patients died.

Relatives are now being asked if they will agreed to their loved ones being exhumed so that the exact cause of death can be established, the Telegraaf said.

Police want to know if the people were killed by cancer or the treatments prescribed by Ross at the Biological Cancer Centre in Bracht, just over the border near Venlo.

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

Two of them were Dutch nationals.

According to media reports, the patients appear to have sought Ross’s help after they ran out of conventional therapy options. He offered a 10-week ‘basic therapy’ against cancer for €9,900, Science said.