West Ham have confirmed the injury of defender James Collins, saying he could be out for up to a month.

Collins injured his hamstring in the Hammers 2-1 loss at Bolton on Saturday and faces up to four weeks on the sidelines.

"West Ham United can confirm that James Collins is likely to be out for four weeks with a hamstring tear in his left leg," read a statement on the club's official website.

"An MRI scan confirmed the injury on Monday afternoon, which means he could miss the best three league games against Manchester City, Wigan Athletic and West Bromwich Albion.

"He could yet be fit for the international fixtures against Finland and Germany in Cardiff on 28 March and 1 April respectively."