41 flats in Hornchurch were evacuated following an explosion yesterday.
10 fire engines and 72 firefighters, as well as police and ambulance crews, attended the incident at the Bridge Point building.
Four people have been treated for minor injuries.
The cause of the blast has not been confirmed.
Essex Fire and Rescue has confirmed an explosion and leak of caustic soda in Thurrock.
It happened at a chlorine scrubbing unit on Oliver Road and Stoneness Road. Five fire engines are on the scene.
One man has received medical treatment, but his injuries are not thought to be life threatening.
Structural engineers are today returning to a West Brompton street, following the collapse of three terraced roofs yesterday. Kensington and Chelsea Council have confirmed the incident, on Fernshaw Road, was not caused by a gas or bomb explosion. Some residents remain in temporary accommodation.
The Health and Safety Executive is investigating the explosion which happened on Pimlico Road in central London, yesterday morning.
"We are aware of this and we are making inquiries into what happened."
"Safety is our top priority and the cause of this incident is being investigated. We apologise to customers for the inconvenience caused by the power cut and our staff restored all supplies as quickly and safely as possible."
The pavement erupted, sending a fireball into the air after a fault on the underground electricity network. 1, 867 customers were affected when power to the area was disrupted. All supplies were reconnected by engineers by yesterday afternoon.
An explosion has ripped through a pavement in central London. No one was injured in the blast yesterday morning. Charlie Brook who lives in Pimlico Road posted this video on YouTube.
It is the largest construction project in Europe, but after a worker was badly burnt on a Crossrail site yesterday, serious questions are being raised about health and safety.
Barry Mcgreham is in a specialist burns unit, after he was injured yesterday when cables were cut through on a Central London site.Now the London Assembly says it's becoming 'concerned' at the 'frequency' of Crossrail accidents. Our Political Correspondent Simon Harris reports
''As is standard procedure on Crossrail following an incident - in this case a cable strike incident - Crossrail has suspended any activity which involves breaking ground such as piling or utility excavation until we are fully confident that it safe to proceed. Such suspensions usually last for several days''