LONDON, Dec 17 (Reuters) - Chelsea said their Women"s Super League game against West Ham United on Sunday has been postponed due to a COVID-19 outbreak in their squad, and Manchester City"s game against Reading has also been called off. Chelsea crashed out of the Women"s Champions League following a 4-0 defeat by VfL Wolfsburg on Thursday, and more cases were identified when the team arrived home, leading to the cancellation of the West Ham fixture. "The decision was agreed between both teams and the FA after a number of positive tests for COVID-19 were returned within the Chelsea FC Women"s team set-up after the last round of testing on return to the UK," the club said in a statement. "Those affected immediately began a period of self-isolation in accordance with Public Health England and Government guidelines. The health and safety of our players, support staff and fans remain paramount." Coach Emma Hayes said following the Wolfsburg defeat that her players, many of whom had to stay in London last Christmas rather than go home to their families because of the pandemic, had been affected by the news that Ann-Katrin Berger and Drew Spence had tested positive before the game. "Our heads were all over the place," Hayes said, before predicting that there would be more positive tests in the squad. Arsenal, who are set to face Birmingham City on Sunday evening, currently top the league on 25 points from nine games, with Chelsea second on 21 points and Tottenham Hotspur third on 17 and Brighton & Hove Albion two points further back in fourth. The WSL winter break is due to start following Sunday"s games, with play resuming again on Jan. 7 when reigning champions Chelsea meet Spurs.