The computer problems which led to flights at Eindhoven airport being grounded and numerous issues at government departments on Wednesday were caused by a software error on a defence ministry network, minister Ruben Brekelmans has confirmed.

The error affected the high security Nafin network which connects more than 180 defence ministry locations and dozens of other official departments as well as the emergency services.

“An error in the software code led to a problem in the network’s time syncronisation,” Brekelmans said. “This made it impossible to join the network. There is no evidence so far that the outage was caused deliberately.”

Most systems were up and running again on Wednesday evening and flights began leaving Eindhoven again around 5 pm.

Brekelmans stressed that the “safety of defence ministry processes” had not been endangered. Experts are now working to establish how the software error happened.

However, RTL tech journalist Daniël Verlaan said it is ‘bizarre’ that it took more than 24 hours to resolve the outage, which first started having an impact on Tuesday evening.

“It is worrying that a software failure can cause such major problems, and it shows our dependence on digital systems which don’t have good backups,” he said. “That is particularly the case with this network, which the government says should be seen as the backbone of our digital society.”

Last year, the national audit office Algemene Rekenkamer began an investigation into the Nafin network’s security, which will be published in two months.

“Vital (digital) infrastructure in Europe is under threat,” the agency said at the time. ”In recent years, incidents of sabotage have become more frequent. The Nafin network is essential for the functioning of the armed forces and the entire central government. Given the threat, this network must be well protected against any cyber attacks.”