The Hammers are joined by Premier League rivals Leeds United and Leicester City in their interest as clubs circle with a view to a summer move.
De Tomas was part of the Espanyol side that were relegated from La Liga in 2019/20 but has been leading the charge to promotion this term.
In 29 Segunda appearances this season, the 26-year-old striker has scored 16 goals and delivered two assists to teammates.
Capped four-times by Spain at Under 19 level, all of De Tomas’ success to date has come in his homeland, having struggled to adapt to life in Portugal following an £18m switch to Benfica from Real Madrid.
Valued at just £9m (Transfermarkt), De Tomas would present a relatively affordable option this summer and perhaps allow for another arrival.
With the Hammers preparing for a season with European competition to boot, there will be the requirement for additional strength in depth.