The British government has ordered an urgent investigation into how a fire at an electricity substation left Heathrow Airport in London in darkness on Friday, crippling one of the world’s busiest airports.

“We are determined to properly understand what happened and what lessons need to be learned,” Britain’s energy secretary, Ed Miliband, said in a statement late on Saturday.

The fire, which the authorities believe was likely accidental, raised questions about the resilience of Britain’s key infrastructure and whether the country has invested enough to maintain it. But some experts said the blackout was probably unavoidable given the scale of the blaze at the substation.

Within hours of the airport going dark, engineering experts were questioning whether Heathrow was supported by infrastructure befitting a major world hub.

Martin Kuball, a professor of physics at the University of Bristol, wrote in an online post that the fire was a warning sign about the nation’s electrical systems.

“Unfortunately, there is no resilience built into the National Grid,” Kuball, a Royal Academy of Engineering chair in emerging technologies, wrote at the Science Media Center. “In part, this is because we still rely on old technology in substations that use copper windings to distribute power rather than new technology, so-called solid state transformers.”

New York Times News Service