Following reports in local media, the state prosecutor in Saarbrücken confirmed that the suspect, identified only as B., was under investigation on five counts of murder and two counts of attempted murder.
Högel, believed to be Germany's most prolific serial killer, murdered patients with lethal injections between 2000 and 2005, before he was eventually caught in the act.
The prosecutor said that B. was arrested in June 2016 after he was caught posing as doctor in an attempt to gain access to a patient in the intensive care unit of a hospital in Homburg, near the French border.
At the time, he had been working at the hospital as a nurse for just six weeks, but was already the subject of an internal investigation for allegedly administering unprescribed medicines.
The 27-year-old is now suspected of committing a number of murders between March 2015 and March 2016, while working at a hospital in nearby Völklingen.
Seven bodies have been exhumed during the investigation, of which six were found with traces of unprescribed and potentially lethal substances including ajmaline, a substance also used by Högel.
B. is currently serving a separate three-year prison sentence for fraud offences.