Dissident republicans were responsible for leaving a bomb outside a County Antrim civic centre, police have said.
The civic centre was staging a performance of a musical
The "crude but viable" device was left in a car outside Lisburn's Island Civic Centre on Thursday evening.
About 350 people had to leave, including the cast and audience at a performance of the musical Carousel, following an anonymous phoned warning.
Army bomb experts dismantled the device and removed it for further examination. Police said it was potentially lethal.
The alert began at about 2010 BST on Thursday when the Samaritans received a phone call using a recognised codeword, warning that a bomb would explode in 25 minutes.
About 350 people were attending various events inside, including children's dance classes and a function in the Mayor's parlour for a group of disabled people.
The area remained cordoned off until 0830 BST on Friday.
Police have appealed for anyone who may have witnessed suspicious activity to contact them.
Condemning the attack, Chief Superintendent Ken Henning said it had "the potential to cause serious injury or worse to any member of the public at the centre".
Patricia Carleton's two grand-daughters were in the show
He said the bombers had nothing to offer the people of Lisburn apart from "inconvenience, disruption and the potential to maim and kill".
He added: "It's an absolute disgrace."
One of those moved from the building, Patricia Carleton, said it was "most unfortunate".
"My two grand-daughters are involved in the show," she said.
"They just had to leave all their clothes, as had all the cast."
Roy McIlwrath of Lisnagarvey Operatic Society which was putting on the show, said they were half-way through the performance when the alarm was raised.
"It was a bitterly cold night and the cast, as you would expect, were out in costume, including about 16 young people appearing in the show," he said.
"Some of them were out in their bare feet, with very little on but the costumes they were wearing - it became a priority to look after them."