The government has launched an urgent investigation into the power shutdown that crippled Heathrow airport, with experts warning it was a “wake-up call” about vulnerabilities in the nation’s critical infrastructure.

The energy secretary, Ed Miliband, has commissioned the independent National Energy System Operator (Neso) to investigate the incident and assess the UK’s energy resilience. The regulator Ofgem warned it would “not hesitate” to take action if there were any breaches of standards or licence obligations.

Heathrow was shut down on Friday after a blaze at a high-voltage substation in Hayes, west London, with more than 1,350 flights disrupted and an estimated 300,000 passengers facing travel chaos. Heathrow airport said it was “fully operational” on Saturday, although disruption to flights was expected to continue for a few days.

Counter-terrorism officers from the Metropolitan police have been leading the investigation into the cause of the fire. Police say that after an initial assessment, they are not treating the incident as suspicious.

Miliband said: “The loss of power to the Heathrow area has caused major disruption to thousands of people and many businesses. We are determined to properly understand what happened and what ­lessons need to be learned.

“That is why, working with Ofgem, I have today commissioned the National Energy System Operator to carry out an investigation into this specific incident and to understand any wider lessons to be learned on energy resilience for critical national infrastructure, both now and in the future. The government is determined to do everything it can to prevent a repeat of what happened at Heathrow.”

Neso was launched as a public body in October, with responsibilty for the managing and planning of electricity and gas networks in England, Scotland and Wales.

Cabinet Office minister Pat McFadden is separately already leading a review of national resilience, which is due to report shortly. A National Risk Register published in January outlined the risk of attacks on the power network or critical failures.

Thomas Woldbye, chief executive of Heathrow airport, said this weekend that a review would examine how the impact on operations from any similar incident could be minimised in the future. He said yesterday he was “proud” of how Heathrow dealt with the incident, but he has been criticised for “complacent” public comments.

“The situation was not created at Heathrow,” Woldbye told the BBC Radio 4 Today programme. “It was created outside the airport and we had to deal with the consequences. Of course, we look at what we can do better.” Woldbye said the airport is supplied by three power substations, but it was necessary to “restructure the supply” because of the fire.

Experts have described the Heathrow shutdown as a “wake-up call” that raised questions about the resilience of power infrastructure supporting other critical sites.

Lord Toby Harris, chair of the independent National Preparedness Commission, said: “I find it extraordinary that the airport has got itself into a position where one substation going out is sufficient to take out the whole airport.” He said the public comments coming from the airport team and Woldbye on the shutdown had been “rather complacent”.

It emerged on Saturday that a consultancy report had warned in 2014 that a “key weakness” in the airport’s infrastructure was the “main transmission line connections”. The warning in the risk assessment study, reported by the Financial Times, stated that “even a brief interruption to electricity supplies could have a long-lasting impact”.

Hundreds of additional staff have been drafted in to help clear the passenger backlog, with the impact on travel arrangements expected to last for days. Farah Rafeeq, 24, who was due to fly to Cambodia with a friend on Friday for a wedding, said: “The last few hours have been nightmarish because it is one of our closest friend’s wedding and we have to travel for at least 20 hours to get there. We had to pay double the amount, between £600 and £700, for the new flight.”

The transport secretary Heidi Alexander said: “Heathrow is a massive airport that uses the energy of a small city, so it’s imperative we identify how this power failure happened and learn from this to ensure a vital piece of national infrastructure remains strong.”

Fintan Slye, chief executive of Neso, said: “Neso welcomes the government’s commission to review the power outage incident impacting Heathrow and surrounding areas. We will now work with all relevant stakeholders to understand the ­lessons that can be learned to improve the future resilience of Great Britain’s energy system.”

Neso is expected to report its initial findings within six weeks.