ITV Studios has been evacuated due to a fire in the building.
The fire began shortly after Good Morning Britain (GMB) began at 6am and the London Fire Brigade confirmed that the situation is "still ongoing".
A message on the GMB Twitter account read: "We've been evacuated because of a fire alarm. Everyone's safe and we're hoping to get back in and on air ASAP."
Guest Holly Brockwell, who was due to speak on GMB, tweeted a picture of smoke pouring out of the window of the studios.
Just before 7.30am, she tweeted: "Tonnes of fire engines, fire still blazing."
Brockwell reported that the fire was in a production suite.
The London Fire Brigade confirmed they had sent several crews to the studios and said the situation was "still ongoing".
GMB co-host Ben Shephard tweeted that the fire appeared to have been extinguished.
He posted: "Five engines and seemingly no more smoke! Not sure if we'll make it back on air yet but hoping to."
A pre-recorded version of GMB was aired before an episode of Dinner Date began just after 7.30am.
Shephard's co-anchor Kate Garraway and news presenter Ranvir Singh apologised to viewers in a video on GMB's Twitter account.
Garraway said: "There's five or six fire engines so they're treating it very seriously, which is comforting, isn't it?"
Singh added: "It's quite a big incident. We're apologising to you because we're meant to be on air giving you lots of interesting stuff to sort your Good Friday."
Garraway finished: "It's really annoying. Honestly, it's all here (points to production notes). It would have been amazing. So maybe we can get back on air and give you a little sum of it later. Happy Easter!"
Shephard posted a photo of them posing with firemen from Soho Blue Watch, writing, "Every cloud!"
The London Fire Brigade Twitter account confirmed that four fire engines and 20 crew had been sent to tackle the blaze.
Their latest tweet read: "GMB off air while we tackle fire at ITV Studios. A room on the 1st floor is alight. 50 people evacuated."