French-Palestinian MEP Rima Hassan was taken into custody on Thursday morning on suspicion of glorifying terrorism, Le Parisien reported.
Hassan's party, La France Insoumise (LFI), has also confirmed it.
The case surrounding the LFI politician reportedly concerns a tweet she posted on 26 March but later deleted.
The tweet was about Kozo Okamoto, a former member of the Japanese guerrilla group Red Army. Okamoto was convicted in Israel for an attack on Israeli Ben-Gurion Airport in 1972, in which 26 people were killed.
The Red Army carried out that attack for the Popular Front for the Liberation of Palestine. He was released from Israel in 1985 as part of a prisoner exchange.
Hassan deleted the tweet after she was summoned by the police, according to Le Parisien. The politician has now reportedly been placed in custody as part of an investigation by the body against online hate, the Pôle National de Lutte Contre la Haine en Ligne (PNLH).
"She has been taken into provisional custody, which is inconceivable considering she has always appeared at all summonses," a source within La France Insoumise told the French news agency AFP.
