A group of Czech artists who inserted a nuclear explosion into a national weather broadcast have been told by a prosecutor they could be sent to jail.
The six hackers are accused of tampering with equipment during a live panoramic shot of mountains last June.
A flash of bright light could be seen followed by a fiery mushroom cloud on the horizon.
The group, who last month won an award from Prague's National Gallery, face charges of spreading false information.
It was the first time the NG 333 prize for young artists was awarded.
The six, who call themselves "Ztohoven", claim that the aim of the project - called Media Reality - was to show how reality can be manipulated by the media.
They say they are not political and do not intend to intimidate society.
But Czech Television, which broadcast the hacked Panorama programme, said the stunt was "very unsuitable and could have frightened a lot of people".
In order to hack into the broadcast, the group is said to have climbed up a television tower near the Krkonose ("Giant Mountains") in the northern Czech Republic and connected a computer to the camera and broadcast cable.
Ztohoven are no strangers to publicity stunts.
When President Vaclav Havel stepped down in January 2003, they covered up part of a neon heart sculpture in his honour at Prague Castle and turned it into a giant question mark.
A state prosecutor in the northern town of Trutnov said that a trial could start this month.
If found guilty, the six could face a heavy fine or a maximum sentence of three years in jail.