The group were saddened by the news of the sudden passing of 16-year-old Magdalena Szablinska - known as Magda - after a suspected heart attack earlier this week, reported Contactmusic.
The teenager had been rushed to hospital after collapsing at a bus stop by her school in London, but doctors were unable to save her.
Harry Styles, who, along with the rest of the group, had met Magda and posed for photos with her, wrote on his Twitter page, "It's incredibly sad to hear the news about Magda. She was so so lovely, I am thinking of her and her family. RIP."
The other three members of the boy band - Zayn Malik, Niall Horan and Liam Payne - have yet to comment.