Arsenal sent their top scouts to Upton Park on Saturday to run the rule over Christian Benteke and Winston Reid, reports the Daily Mail.
The Gunners are in the market for a new striker in the January transfer window with Olivier Giroud representing their only in-form striker.
The same publication revealed last week that Arsenal were ready to move for the Belgian striker when the window reopens, with Aston Villa wanting £28m for the player.
Ahead of a potential January move for the 22-year-old, Arsene Wenger sent his best men to West Ham to get a better idea of whether Benteke can cut it at the Emirates.
But Benteke wasn't the only focus for the Gunners.
They also took the opportunity to scout Winston Reid, who has been linked with a £6m move to Arsenal in recent days.
The New Zealand international was awarded West Ham's Player of the Season last year and has continued that impressive form this term.
Thomas Vermaelen, who has struggled for form over the last 12 months, has been linked with an exit from Arsenal and Wenger wants Reid to fill Verlmaelen's boots should he leave.
Arsenal continued their impressive start to the season yesterday, beating second placed Liverpool 2-0 to go five points clear at the top.
However, a 2-0 reverse against Chelsea in the Capital One Cup earlier this week exposed a lack of depth in the squad, reiterating the need for Wenger to sign reinforcements in January.