The Boro chief is looking to bolster his squad, with Paris St Germain midfielder Didier Digard one player expected to move to the Riverside.
Boro chief executive Keith Lamb would not identify their targets, but is keen to have the players on board in time for pre-season training.
Lamb told the club's official website: "We are actively pursuing a number of players.
"Negotiations are going very well and we hope to have most of our incoming transfer activity completed before the players return to training on July 7.
"Everything is going well and we are confident of completing two or three new signings soon."