(LONDON) — London’s Heathrow Airport is now “safely able to restart flights” after a fire at a nearby electrical substation closed one of the world’s busiest airports on Friday.

However, even as the airport says it can restart flights, officials advised people not to travel “unless your airline has advised you to do so.” The airport said it hopes to “run a full operation” on Saturday.

“Our teams have worked tirelessly since the incident to ensure a speedy recovery. We’re now safely able to restart flights, prioritising repatriation and relocation of aircraft,” Heathrow said in a statement.

Heathrow Airport said the fire at the substation, which supplies power to the airport, caused a “significant power outage” and the airport was expected to be closed until 11:59 p.m. local time on Friday night.

“We expect significant disruption over the coming days and passengers should not travel to the airport under any circumstances until the airport reopens,” a spokesperson for Heathrow Airport said.

In total, 70 firefighters and 10 fire trucks responded to the blaze in west London when the London Fire Brigade brigade was first called at 11:23 p.m. local time. The fire was contained more than seven hours later at 6:28 a.m. on Friday morning, but was still burning at about 10% on Friday evening.

“This was a very visible and significant incident, and our firefighters worked tirelessly in challenging conditions to bring the fire under control as swiftly as possible,” London Fire Brigade Assistant Commissioner Pat Goulbourne said. “Thanks to their efforts and coordinated multi-agency response, we successfully contained the fire and prevented further spread. “We will maintain a presence at the scene throughout the day, assisting the National Grid as they assess the site.”

Firefighters safely evacuated 29 people from neighboring properties and, as a precaution, a 200-meter cordon was established with around 150 people evacuated.

“Due to the significant smoke, we strongly advise local residents to keep their windows and doors closed, as some smoke will remain for a number of hours today. Scientific advisors will also be on-site this morning to conduct further assessments and monitor the air quality,” Goulbourne continued. “Our Control Officers handled more than 200 emergency calls, providing guidance and reassurance to the public. As the morning progresses, disruption is expected to continue, and we urge people to avoid the area whenever possible.”

Counter-terror police were on the scene at the Hayes substation, London’s Met Police confirmed to ABC News, but they cautioned it’s only because they could get the investigation done faster.

“We are working with the London Fire Brigade to establish the cause of the fire which remains under investigation. While there is currently no indication of foul play we retain an open mind at this time,” Met Police said in a statement. “Given the location of the sub-station and the impact this incident has had on critical national infrastructure, the Met’s Counter Terrorism Command is now leading enquiries.”

As many as 290,000 passengers could be impacted by the closure Friday, according to Cirium, an aviation analytics company. There were 665 flights scheduled to depart from Heathrow on Friday, with 145,094 seats. There were 669 flights scheduled to depart to Heathrow on Friday, with 145,836 seats, according to Cirium. The fire could affect another 270,000 passengers on Saturday, too, Cirium said.

“Accordingly, the impact of this incident can cascade over several days, as aircraft, crew, passengers are out of place, with limited spare aircraft and seats available to recover passengers,” Cirium said in a statement.

British Airways, which has a hub at Heathrow Airport, said it is advising travelers not to go to the airport and that they are working to notify passengers of their travel options for the next 24 hours and beyond as soon as possible.

Meanwhile, inbound flights to Heathrow are being redirected to other U.K. airports, officials said.

“Due to a power outage in the London Heathrow area, London Heathrow Airport is currently closed,” British Airways said. “As a result, customers due to travel from Heathrow on Friday are advised not to travel to the airport until further notice. This will clearly have a significant impact on our operation and our customers and we’re working as quickly as possible to update them on their travel options for the next 24 hours and beyond.”

The fire has caused a power outage affecting a large numbers of homes and businesses and led to some evacuations, the fire brigade said. Firefighters led 29 people to safety from neighboring properties and, as a precaution, established a cordon around the area and evacuated about 150 people.

“This is a highly visible and significant incident, and our firefighters are working tirelessly in challenging conditions to bring the fire under control as swiftly as possible,” Pat Goulbourne, assistant commissioner of the London Fire Brigade, said in a statement shortly before 2 a.m. local time.

The cause of the fire is not yet known, the fire brigade said.

ABC News’ Clara McMichael and Ayesha Ali contributed to this report.

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