Drone footage shows the debris of a building that hospitalised four people.

Four builders were taken to hospital with minor injuries and others escaped before the emergency services attended the scene.

The construction workers were rescued from the courtyard of the property and the wall is said to have fallen as the roof, front and rear walls were unsupported.

READ MORE: High Street closed after building collapses

The road was blocked off as the authorities as there was fears the three-storey terraced building would damage the shops it was connected to.

Firefighters from Watford attended the scene, along with colleagues from Garston, St Albans, Rickmansworth and Potters Bar fire stations.

The video from the drone shows that the roof entirely collapsed at the front and half has been teared down at the back, as well as damage to the top floor.

The shop was in the process of being renovated when the incident happened, and around 50 people were evacuated from the surrounding shops.

A health and safety officer was called yesterday to assess the safety of the building, which may have to be pulled down to stop it affecting the other buildings.

Smoke was seen to be pouring out from the gap beneath the red door by a passer-by and employees in Tweens Pharmacy heard a noise but did not realise the severity of the situation.

The shop had been used to sell antiques but had been closed since at least 2002.

It is said to have recently been bought and was supposedly going to be used as a cycle shop.

Gas and electrical suppliers were also called to the scene to help prevent further damage.

The road has remained closed for the day and last night bus routes that used the road were cancelled.