Didn't see this mentioned elsewhere.

I was heading from Epping into London just before midday today. We were
held at Leytonstone for a good 15 mins as we were advised that the passenger
alarm had been activated on a train at Mile End and control had instructed
the driver to stay put. We then got on the move again but at Stratford, the
driver told us all to disembark due to a Central line train on fire at
Liverpool St. The train then headed empty westbound towards Mile End.