Two students have apologised after entering a fancy dress competition dressed as New York's Twin Towers under attack.
Amber Langford and Annie Collinge, both 19, scooped £150 in shopping vouchers after winning the contest at Rosies nightclub in Chester.
Photographs published by The Sun show that their outfits depicted flames and explosions during the terror attack on the World Trade Centre on September 11 2001.
Their costumes - which were labelled North Tower and South Tower - also portray planes hanging from the buildings.
Ms Langford's father, pilot Martin Langford, told The Sun: " I didn't know anything about it, but I'm not happy at all.
"She knows I'm a pilot and that's not cool at all. We will be having a little chat, I think."
The University of Chester students, who entered the horror-themed fancy dress competition on Halloween, told the newspaper: " We never meant to be offensive, but we apologise if any offence was caused.
"The idea was to depict a serious, modern-day horror that happened in our lifetime and was not intended as a joke."
A spokeswoman for the Stonegate Pub Company, which runs the nightclub, said: " Following the club night Halloween promotion that took place at Rosies, Chester, we are extremely concerned that an award of shopping vouchers was made to two young women who were dressed in a distasteful and offensive manner.
"There was a serious error of judgment made on the evening by a contracted DJ to award such a prize and we apologise to anybody who may have been upset or offended by this. A full investigation by the company is taking place."
The University of Chester and Chester Students' Union said in a joint statement: "We utterly condemn the appalling photos. Both organisations have begun an urgent investigation with a view to taking the necessary action."