The woman killed herself in her cell either late Sunday or early Monday, the cantonal department of training and security said in a news release.
“The body was discovered on Monday morning by prison guards,” George Seewer, head of the service for the application of penalties and measures, told local newspaper Le Nouvelliste.
He said such an occurrence was rare in Valais.
“In my career, it is the first time I have confronted a suicide in prison,” Seewer said.
Prosecutor Marie-Line Voirol Revaz confirmed that the woman had been placed in temporary detention after the discovery on July 22nd of her partner’s body in an apartment at Saint Gingolph, a small town in Valais on the south side of Lake Geneva.
Valais police arrested the woman on suspicion of killing her companion.
The death was initially reported by the woman who said that she discovered her lifeless partner after being absent for a few days, police said earlier.
During questioning the woman later admitted to beating her partner on the head with an unidentified object on July 5th, police said.
She left the apartment and for the next 16 days neighbours in the apartment believed the couple were on holiday, according to an earlier report from 20 Minutes newspaper.
The newspaper cited neighbours who said the man was separated from his wife and met his partner, originally from Eastern Europe, in Germany.
Neighbours believed that the man, who had owned the apartment in Saint Gingolph for around 40 years, had wanted to leave his partner, 20 Minutes reported.
The prosecutor’s office has launched an investigation into the suicide.