The blackout quickly spread to other regions, including the Basque country, Andalusia, Extremadura, and Aragon. The root cause of the problem was later found to be connected with a scheduled network upgrade by phone giant Telefonica. The upgrade, which had begun at 3:00 am, caused an MPLS (Multiprotocol Label Switching) system breakdown - a key part of the telecom infrastructure that delivers landline data services and emergency call systems. On the Downdetector platform, about 72% of the complaints were related to fixed broadband. The other 18% complained about a lack of mobile coverage, and 10% complained about loss of service. The outage affected major operators such as Movistar and O2, both of which belong to Telefonica, and cut off thousands of users from internet and phone coverage during the early hours of the morning. Emergency phone numbers were the most affected service. In response, alternative emergency numbers were provided in different parts of the nation.