The cellular network run by Pelephone, Israel’s second-largest provider, was largely inoperative for more than four hours on Sunday, prompting experts to suspect that the disruption was the result of a cyber-attack.

However, the company on Monday morning denied that the lack of service was the result of deliberate sabotage.

Pelephone CEO Gil Sharon told Channel 10 that “We don’t know exactly what happened; it was a technical malfunction, but we know it wasn’t a cyber-attack.” He noted that the network has a system that would isolate any hacking attempt.

Customers around the country began to complain early Sunday evening that they were unable to send or receive phone calls or text messages. Four and a half hours later, Pelephone said that service had been restored to some 90 percent of its customers.

According to the company, the problem was caused by a centralized failure in the main switches and backup systems that transfer calls through the network. The system’s data services were not affected, and users could still access email and the web via their smartphones.

But Pelephone, and all of Israel’s other cellphone networks – as well as the companies that provide electricity, water, gas, banking and credit services, along with just about every other computerized component of modern society — are all at extreme risk of cyber-attacks.

But online threat expert Daniel Cohen said that despite Pelephone’s assertions, he wouldn’t be surprised if this did turn out to have been a cyber-attack. “These companies are constantly fending off attacks, and the hackers know exactly how to target their victims, how to worm their way in, and how to get to the high-level controllers that can take down a cell network, electrical grid, or anything else they want,” said Cohen, the Director of Business Development & Knowledge Delivery at RSA (the Security Division of EMC).

Pelephone has around two and a half million customers. In 2010, Cellcom, the leading cellphone service provider, went down for several hours. The cause of that malfunction was never resolved. 

Pro-Palestinian activists have successfully hacked government as well as bank and hospital sites in the past. Israel has set up a cyber-warfare unit to combat hacking which has reportedly has repelled millions of attempts to cripple websites.

AP contributed to this report.