German prosecutors have said they believe a former nurse may have murdered at least 100 people at two hospitals.

Investigators believe Niels Högel systematically administered fatal doses of heart medication to patients in his care.

His aim was induce heart failure before resuscitating the patients in a bid to impress his colleagues.

Högel is currently serving a life sentence for the murder of two patients - however the investigation into his actions was widened when he admitted killing up to 30 people during his trial.

Widened investigation

Some 130 former patients have since been exhumed by investigators searching for traces of medication that could have been used to shut down their cardiovascular systems.

In late-August, authorities said they believed he may have killed at least 84 other people.

It is now believed Högel may have killed 38 patients in Oldenburg and 62 in Delmenhorst between 1999 and 2005.

Investigators have said he may have been responsible for more deaths - however a number of his potential victims have since been cremated.

If found guilty of all the deaths, he would become one of the worst serial killers in German criminal history.