A major power outage at London's Heathrow has prompted the authorities to close the airport disrupting hundreds of flights around the world and stranding thousands of travelers who are now scrambling for alternatives.

One of the world’s busiest airports was forced to close on Friday after a giant fire at a nearby electricity substation knocked out power there.

The travel chaos rippled across the globe as the airport ground to a halt, forcing aircraft to reroute to other European cities or turn around in midair.

At least 1,350 flights that were scheduled to arrive at or depart from the airport have been affected so far, per the flight-tracking service Flightradar24.

Heathrow officials say the disruptions are expected to last for days as airlines struggle to rebook passengers.

The airport also acknowledged in a separate statement that it was unclear when exactly the power would be restored, warning that it expects "significant disruption over the coming days,"

The cause of the fire is unknown, although security sources indicated there was no immediate indication of foul play.

According to the British media, counter-terrorism officers from London's Metropolitan Police are also investigating the fire as a “precautionary measure.”

London fire brigade was called shortly after power also cut to thousands of homes. More than 70 firefighters tackled the blaze, which the brigade said at 8am was under control.

National Grid U.K. said Friday that roughly 5,000 customers were without power in the impacted area.

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