A large section of the white cliffs of Dover has collapsed into the English Channel following a "substantial" rockfall, according to the coastguard.

Tonnes of the cliff face sheared off near an area known as Crab Bay, but no one was injured.

Dover Coastguard said a full survey had yet to be carried out to determine the exact amount and length of cliff that crumbled on Friday.

The collapse may have been caused by rain freezing and expanding after being absorbed into the chalk, causing it to weaken.

A Dover Coastguard spokesman said: "We can see the start of it from where we are based but then it goes round the corner.

"It appears that it crumbled from the top at high water so there was no one down below at the time. It was quite a substantial fall.

"No one was injured but it does serve as a reminder that if people are walking along the cliff-top or underneath, that the cliff can crumble away.

"Over the years and around the country, including along the coast at Beachy Head in East Sussex, cliffs can fall after water expands when there have been freezing conditions."

The Kent landmark, popularised by Dame Vera Lynn's wartime song The White Cliffs of Dover, has suffered large rockfalls before, most significantly in January last year.

When the cliffs tumble, locals describe it as "like a lorry going down the hill".

Sam Wydymus, 40, co-owner of the nearby Coastguard pub, said: "I have seen pictures of the rockfall and the most noticeable thing is you can see this big patch of white on the cliff-face.

"We didn't hear anything when it fell but it was big enough for people round here to be talking about it. The last major cliff-fall was in January last year when every emergency service turned up.

"That happened during the day and was quite scary, with people screaming on the beach saying it had fallen. When the cliff does fall, it is quite muted and sounds like a lorry going down the hill.

"There isn't any physical warning beforehand. When it happens, it just happens."

A spokeswoman for the National Trust – which looks after parts of the chalk grassland in the area – said the cliff-fall happened between Langdon Cliffs and South Foreland Lighthouse.

She said: "To alert walkers, the National Trust has sited several warning signs at several starting points of the walkways on to the cliffs."