Manchester United have taken up the option to extend the contracts of three players until 2019, the Manchester Evening News have reported.
The club have triggered clauses in the contracts of Daley Blind and Ashley Young, both of whom were out of contract at the end of this season.
Young has established himself as first-choice at left-back this campaign, starting 20 Premier League games and regularly keeping both Blind and Luke Shaw out of the side.
Blind, meanwhile, has hardly featured since the first month of the season and may still depart in the summer should United receive an adequate fee.
Goalkeeper Sam Johnstone has also been given an extension as United look to tie down the immediate futures of a number of players.
The 24-year-old has impressed on loan at Aston Villa in the Championship but is yet to make his debut for Mourinho's side.
Three players remain who could still leave the club on a free transfer in the summer: Marouane Fellaini, Zlatan Ibrahimovic and Michael Carrick.
United previously took up the option of a further year in Ander Herrera, Shaw and Juan Mata's deals, and Mourinho suggested that Shaw could be handed a long-term deal.
"With Luke it is not about changing my mind," said the Portuguese coach earlier this month. "With Luke it's just the evolution or no evolution of his potential like I think you say, fulfilling his potential. It's just about that.
"Because I know Shaw since he arrived in the Premier League with Southampton and I know his potential, his quality.
"He's now for a few months freer of his minor injuries that sometimes stop evolution and I'm really happy so I think the natural consequence of it is that he will have his contract and he will be a Manchester United player for years."