West Ham joint-chairman David Sullivan has told supporters a fifth signing can be expected in the next 72 hours.
A number of Championship clubs are keeping tabs on Leyton Orient defender Mathieu Baudry, Sky Sports understands.
Striker Robbie Findley has had his contract with Nottingham Forest cancelled by mutual consent.
The 27-year-old United States international started only 14 games for Forest during an injury-disrupted two-year spell with the club.
He scored six goals during his time at the City Ground, three of which came in the League Cup.
Forest chairman Fawaz Al Hasawi said: "I would like to thank Robbie for the service he has given Nottingham Forest and wish him every success for the future."