The group confirmed on Twitter today (July 27) that they had almost finished a new song.
"Just in the studio finishing up one of our tracks :-) Sending you a Big Hello from us!!! XxX," the former Sugababes said on Twitter.
Rumours of the reunited threesome's new name emerged earlier this month when a legal trademark document surfaced on the web.
They made their return official on Friday. Buchanan quipped that she had been trying her best to "keep this one on the DL".
Heidi Range, who leads the current incarnation of the Sugababes, told Digital Spy that she knew last year that Mutya Buena, Keisha Buchanan and Siobhan Donaghy had been working together.
She added of her own group: "We're all writing in the studio... It's kind of ongoing. But there's no plans to bring anything out this year."
Watch the Sugababes perform 'Overload' on Top of the Pops below: