The Spaniard has already sealed a permanent transfer for Norwich defender Daniel Ayala and loan deals for Chelsea youngsters Kenneth Omeruo and Nathaniel Chalobah.
However, he will continue his search for reinforcements ahead of Friday night's deadline.
Karanka told the club's official website: "We are looking at all options.
"The objective of the club is to strengthen the squad and my aim is to finish the transfer window with a stronger squad than we had before it started."
Karanka has also handed some of his fringe players the chance to play first-team football elsewhere with Adam Reach, Luke Williams, Richie Smallwood and Andy Halliday all having gone out on loan.