Hainault station has been shut by police after multiple people, including two police officers, were attacked.
Footage on social media shows someone wielding a samarai sword in the area, before police said a 36-year-old man was arrested.
Meanwhile, there are major delays on the M26 into London on due to emergency repairs.
Six-mile queues were reported on the M26 Westbound at the M25 due to a lane closure, traffic monitoring service Inrix said.
The repairs were also causing delays on the M25 in both directions between J5 for Sevenoaks and the Clacket Lane Services.
There are also minor delays on the Circle and Northern Lines due to train shortages and cancellations.
While hundreds of Border Force officers at Heathrow Airport are on the second day of their four-day strike. There is a warning passengers could face longer queues as more than 300 members of the Public and Commercial Services union continue their walkout, affecting Heathrow terminals 2, 3, 4 and 5, in a dispute over working conditions.
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South Western commuter route hit by signal failure
South Western Railway routes between Waterloo and Shepperton are disrupted due to a signalling fault.
Train services running to and from these stations will be suspended between Shepperton and Fulwell.
Disruption is expected until 6pm, says National Rail.
Thameslink routes affected by earlier points failure at New Barnet:
Brighton to Cambridge and Horsham to Peterborough.
Great Northern routes affected by earlier points failure at New Barnet:
Moorgate to Welwyn Garden City and London Kings Cross to Cambridge / Ely / Kings Lynn.
Disruption to Kings Cross trains
Two train lines which go between Stevenage and London Kings Cross are disrupted because of an earlier points failure at New Barnet. The following routes are affected:
- Great Northern between Peterborough / Kings Lynn and London Kings Cross, and also between Welwyn Garden City and Moorgate
- Thameslink between Cambridge and Brighton, between Peterborough and Horsham, and also between Welwyn Garden City and Sevenoaks
Lines have reopened but may still be cancelled or delayed by up to 10 minutes.
This disruption is expected to last until at least 11am.
Elizabeth line no longer delayed
The Elizabeth line has reutrned to running a good service.
British Transport Police on Hainault closure:
The British Transport Police said: "Officers were called to the area near Hainault underground station at 7.07am today (30 April) to assist Metropolitan Police.
“Officers are currently in attendance. The station is closed and a cordon is in place."
The Standard is looking into what impact this violence will have on transport today.
What have police said about the Hainault incident?
Police have released a full statement on the incident which closed Hainault station:
Minor delays to Elizabeth line
There are currently minor delays between Paddington and Heathrow due to an earlier person ill on a train at Whitechapel - good service on the rest of the line.
'Multiple stabbings with samurai sword' at Hainault
There are unconfirmed reports of multiple stabbings and footage at the scene appearing to show a man with a samurai sword.
A large police presence was seen outside Hainault tube station.
Labour MP for Ilford North Wes Streeting said a “critical incident” has been declared following the incident asking for people not to speculate or post footage on social media “until details are confirmed.”
Read more here.
Crash on M25
There is currently queueing traffic due to traffic signal failure on A12 both ways at the M25 J28 (Brentwood/Brook Street Roundabout).
Congestion to M25, five miles anticlockwise back past J29 Romford, and a couple of miles on the A12 Brentwood Bypass.