The original Sugababes have cemented their comeback by releasing their first single online. Mutya Keisha Siobhan's Flatline premiered on various streaming websites on Thursday (04Jul13) and will be made available as a download on 1 September (13). British singers Mutya Buena, Keisha Buchanan and Siobhan Donaghy formed in 1999 and enjoyed several years of pop success before breaking up to follow solo careers. All three members had abandoned the group by 2009, but they reunited as Mutya Keisha Siobhan last year (12). Billboard.com reports the group will travel to Los Angeles later this month (Jul13) to film the video for Flatline.