The 28-year-old collapsed with 15 minutes remaining of Cameroon's Confederations Cup semi-final victory against Colombia in Lyon.
The thoughts of everyone at the club are with Marc's family at this very sad time. He is fondly remembered by club staff and former team-mates as a friend and colleague.
Marc-Vivien was a record signing for West Ham in Harry Redknapp's reign, and Glenn Roeder, who worked with him on the training ground, said in an interview in September 2002: "I really liked Marc-Vivien Foe as a man; I thought he was a wonderful human being - to be honest, he was a delight to be around".
An official club statement will follow shortly.