BERLIN — A criminal investigation into an artist who built a partial replica of Germany’s national Holocaust memorial next to the home of a far-right politician has been formally closed, more than 16 months after it began but less than a week after its existence became public.

Reverberations from the inquiry into the artist, Philipp Ruch, and his collective, the Center for Political Beauty, have continued to spread. On Thursday, a letter was released from more than 100 prominent German cultural figures, academics and politicians expressing “disbelief” at the investigation, which employed a legal provision more often used to monitor gangs, extremist groups and terrorist cells.

The letter demands an apology and an explanation from those who undertook the investigation, and calls on them to disclose any political links: Martin Zschächner, an attorney for the state of Thuringia who was in charge of the case, has been accused by the left-wing politician who uncovered the inquiry of being soft on far-right offenders.

The outcry has come after a public discussion about right-wing activists in positions of public authority, and after several publicized cases of extremists among police and army officers.