Mills isn't yet fully recovered from the shin splits injury suffered while on loan with City earlier in the season, but with the deadline looming it is now or never for a deal to go through.
Tigers boss Phil Brown told the Hull Daily Mail: "I have spoken to him and he'd like to come back and we'll explore that avenue throughout this week.
"Danny is an option and we may get hands on him before the deadline. I've spoken to him since he's left as I felt he did a great job here and have kept in touch as a matter of course."
Brown also says he is talking to other Premiership managers about potential signings.
City already have Dean Windass, Ricardo Vaz Te and Lee Peltier on loan, so Brown is able to play up to two more loanees in a league match. Windass's loan deal is expected to become a permanent transfer in the summer.