Eurotunnel passengers experienced bank holiday disruption after smoke was spotted on a works train in the Channel Tunnel.
The tunnel was closed for about 45 minutes following the incident at 5.30am UK time on Monday, but there then remained some "residual delays" to services.
A Eurotunnel spokesman said: "Some smoke was seen on a works train, one of the engineering trains we use for maintenance.
"Precautions required that we shut everything down and check. We did exactly that and it turned out to be nothing more than a bit of smoke from some engineering equipment."
He denied reports that there was a fire, and added: "The tunnel was closed for about 45 minutes just to clear everything out. The train is out of the tunnel now.
"We have been building up services and at 10am everything was returned back to normal."
A Eurostar spokesman said "two or three" services were slightly delayed but operations were running normally.