The sign caused 21 riders to be injured in the collision.
Tour de France organisers have said they are suing a spectator who caused a crash after German cyclist Tony Martin rode straight into a sign being held out by a fan.
The spectator was looking the other way at a television camera when the cyclist crashed into the sign, causing a crash that injured 21 riders and now the organisers are looking to take legal action against the spectator, according to Reuters.
The spectator's cardboard sign read "Allez Opi-Omi" which translates to "come on grandad-granny", in a mix of French and German.
The incident saw 21 riders injured in the ensuing collisions, with 47km left of the 198km stage from Brest to Landerneaustage.
It was the first of two huge crashed during the event on Saturday as another massive pile-up with roughly 7km left saw four-time champion Briton Chris Froome and others impacted.
The initial crash also claimed the race's first victim, with German Jasha Suetterlin of Team DSM having to leave the Tour due to the injuries he sustained.
Frenchman Julian Alaphilippe recovered from a crash to win the first stage of the Tour, meanwhile, Australian Michael Matthews took second place and Slovenian Primoz Roglic came third.
