Neither of the midfield pair were pictured in training on Wednesday afternoon and both have been left out of the travelling squad.
Jones was also absent for Liverpools draw against Luton at the weekend with a minor fitness issue, This Is Anfield understood.
Klopp has now provided an update, saying the 22-year-olds issue is a hamstring problem. Curtis had last week a hamstring [problem], not massive.
After the international break, he will be back, but not before. Low, low grade hamstring.
The manager added: When I took him off vs. Bournemouth he didnt feel anything, then I came in the dressing room and he said he felt something.
Ryan Gravenberch was a surprise omission from training on Wednesday and, having started all three of Liverpools Europa League matches this season, will miss the Toulouse game.
He is also a doubt for Sundays match vs. Brentford, with Klopp explaining: Ryan got a little niggle knee. He was running today (Wednesday) already, but there was no chance for this game.
There is a chance for Brentford and he will definitely be back after the international break.
Jones and Gravenberchs absences mean we will probably see a midfield three of Wataru Endo, Harvey Elliott and Alexis Mac Allister against Toulouse.
The latter should start given he will miss Sundays Premier League match against Brentford due to suspension.
With Dominik Szoboszlai having played more minutes than any Liverpool player this season except Salah, the Hungarian is due a rest.
Additionally, Thiago and Stefan Bajcetics absences effectively mean that Liverpools midfield picks itself.
An outside shout to come in is James McConnell, who made his debut in the final moments of the latest Europa League game at Anfield.