Southern Television and Thames Television were blacked out as a pay dispute involving behind-the-scenes staff escalated.
Other ITV regions were expected to be hit, and the entire network was in danger of facing a total shutdown.
Nine members of staff were suspended, spokesmen for the stations said.
Thames and Southern went off air in the evening and failed to restart the following morning.
Southern said it had suspended three electricians who had been operating an overtime ban.
Other electricians walked out in support, and members of the Association of Cinematograph, Television and Allied Technicians refused to operate equipment without them.
The company was hoping to arrange talks between management and the unions.
Journalists at Southern were unsure whether they had been suspended after a row between three of the four unions at the Southampton studios.
A spokesman from the National Union of Journalists at Northam said until talks were over and the situation clear, journalists would continue to work normally.