Hammers tracking Spanish striker
The Hammers are said to have sent scouts to watch the 23-year-old in action during Saturday’s Catalan derby, in which Espanyol held Barcelona to a 0-0 draw.
Blackburn and Wigan are also believed to have expressed an interest in the talented frontman, but are considered to be outsiders to land his signature.
Espanyol have already revealed that they will be willing to part with Callejon over the summer, if the price is right.
They rejected an offer of €4million (£3.5m) during the January transfer window, but would have had to pass 15% of that fee onto Real Madrid.
The capital giants included such a clause in Callejon’s contract when they offloaded him in 2008.
However, that agreement is set to expire on 30th June, meaning Espanyol will keep 100 per cent of any fee generated.
That has convinced them that the time may be right to sell, with reports suggesting a €5million (£4.4m) offer would be enough to force their hand.