Families have been told to close their windows and doors as some 100 firefighters tackle a huge blaze in a London suburb.

Crews dashed to reports of a fire affecting a range of railway arches and businesses, including vehicle workshops, situated within the arches near Roxeth Green Avenue in South Harrow, northwest London at around 1.30am. They remain at the scene, and have advised residents to keep windows and doors shut due to the smoke.

Piccadilly Line services on the London Underground are impacted by the fire, London Fire Brigade (LFB) warned. The service added: "People in the local area are being asked to keep their windows and doors closed at this time due to smoke travel.

"Road closures are currently in place in Roxeth Green Avenue, near the junction of The Arches, and are expected to remain in place throughout the night. The Piccadilly Underground line, which runs over the railway arches, is expected to be severely impacted when services are due to resume in the morning."

The section between South Harrow and Uxbridge on the Piccadilly Line is part suspended, while there are severe delays westbound between Acton Town and South Harrow due to the fire. London Underground tickets are being accepted on local bus services.

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Photographs shared on social media show large plumes of smoke billow from the fire. The cause of the fire remains unclear at this stage. Authorities will investigate this as part of the operation. The LFB spokesperson continued: "The Brigade received the first of around 40 calls about the fire at 0118 and mobilised crews from Harrow, Wembley, Stanmore, Ruislip and surrounding fire stations to the scene.

"Two 32-metre turntable ladders are also attending and they are being used as water towers to help extinguish the fire from above. A drone has also been deployed, providing the Incident Commander with a greater situational awareness of the incident."

Roxeth Green Avenue connects the Northolt Park area in the southwest to the Roxeth area of Harrow in the north. It runs underneath the Piccadilly Line near the junction with The Arches, an industrial road which takes traffic northeast towards Rayners Lane.

It mirrors a similar blaze in Hertford last month, following which families there had to close their doors and windows too. Smoke could be seen billowing "from quite a distance" after the blaze on Pegs Lane in Hertford. Crews in six fire appliances attended after several calls to Hertfordshire Fire and Rescue Service.

"Six fire appliances are in currently attendance at a fire on Pegs Lane, Hertford. Please keep roads in the immediate area clear to allow emergency services to reach the incident as efficiently as possible. There is a large amount of smoke from the fire, so if you live nearby please keep windows and doors closed while we deal with the incident," a spokesperson for Hertfordshire Fire and Rescue Service had said at the time. The operation on the street, which is in the centre of Hertford and near several office blocks, lasted several hours.