Commuters have been hit with delays to several Tube services during rush hour on Monday evening.
There is minor disruption on the Overground between Willesden Junction and Stratford.
On the Underground, the Central and Piccadilly Lines are both delayed.
Meanwhile, around 150 M25 maintenance workers employed by Balfour Beatty are being balloted for strike action over pay, Unite said.
The workers, who are responsible for the maintenance of the entire M25, are angry at Balfour Beatty’s pay offer of 3.4 per cent. With the real rate of inflation, RPI, at 4.9 per cent this is a real terms pay cut. Increasing tensions, is the fact that the workers also received a below inflation pay rise last year.
The workers will begin balloting this week and the vote will close on March 12, with industrial action expected soon after.
