The Whites are searching for forward cover with Richard Cresswell unlikely to play again this season after undergoing knee surgery and Gray is out of the first team picture at Sunderland.
With the change in manager on Wearside, Kevin Ball took over from Mick McCarthy last week, he is now surplus to requirements and Ball is believed to be happy to loan the player out for the remainder of the season.
The 28-year-old, who joined Sunderland last summer from Sheffield United in a £1.1m deal, is the son of former United defender Frank and nephew of Elland Road legend Eddie.
He started his career with Leeds as a youngster and made 28 appearances between 1995 and 1998 before being sold to Bury.
Since leaving Elland Road, the Harrogate-born Scotland international has had spells with Bury, Nottingham Forest, Preston, Oldham Athletic, Bradford City, Sheffield United and Sunderland.
He scored 25 goals in 65 appearances for the Blades before his switch to Sunderland.
Gray can either play up front or on the right flank, and his presence would increase Blackwell's options.