At least one person is missing after a crane fell on to houses in east London, leaving four people injured.

London Fire Brigade (LFB) said the crane collapsed on a site where flats are being constructed, and crashed on to two adjacent terrace houses on Compton Close, Bow, on Wednesday afternoon.

A video posted on Twitter showed a terraced house with part of the roof caved in, and emergency services said “a complex rescue operation” is under way which is likely to take some time.

London Ambulance Service (LAS) said crews have treated four people at the scene, while a spokesman for the LFB said there are reports of at least one person being unaccounted for.

A spokeswoman for LAS said: “We treated two of these patients for head injuries and took them to hospital and we assessed the other two patients at the scene.

“We are working closely with other members of the emergency services at the scene with more updates to follow.”

LFB assistant commissioner Graham Ellis said: “Our urban search and rescue crews are undertaking a complex rescue operation and using specialist equipment to search the properties.

“There are reports of at least one person that may be missing and unaccounted for in the houses.”

The crane that collapsed was being used by Swan Housing Association and NU living.

A spokeswoman for Swan Housing Association and NU living said: “Swan Housing Association/NU living is aware of an incident that occurred at our Watts Grove development site in Tower Hamlets, east London, this afternoon.

“A full incident response has been implemented and our staff are on site supporting the emergency services in their response.”

Work on the Watts Grove site began in 2018 and the one, two and three-bed shared ownership apartments are replacing an electrical substation building, according to the NU living website.

Neil Marney, chief executive of Marney Construction, said his company was working on another site and he could see the crane being erected on Tuesday.

He told the PA news agency: “My project manager on the site called me immediately and said the crane you were looking at yesterday being erected has just collapsed.

“So all I could see yesterday was the mast and the cab was on, and then I believe they started to add sections of the boom.”

The crane that collapsed was not one of Marney Construction’s cranes nor was it a crane on one of its sites.

Properties either side of the incident have been evacuated.

The Metropolitan Police sent officers to the scene after they were called at around 2.39pm on Wednesday to Gale Street to a report of a crane that collapsed into a residential property and a building site.

Unite national officer Jerry Swain said there must be “an urgent, full and complete investigation into the circumstances that led to this accident”.

He added: “The preliminary findings of which must be released in weeks, rather than months or years, in order to ensure that similar accidents are avoided in the future.”