A safety watchdog called in to examine what caused an office block in Hounslow to collapse yesterday says it may not launch a formal investigation.

A huge chunk of the seven-storey Hounslow House, beside Hounslow bus station in London Road, came crashing down as it was being demolished yesterday at about 4.40pm.

Debris was sent crashing to the ground, breaching the wall of the bus station, which had to be evacuated, and police cordoned off London Road as thick plumes of dust filled the air.

The road was open as normal today after a section of the building's facade hanging at a precarious angle was removed to make the site safe.

A spokesman for the Health & Safety Executive (HSE), which investigates serious workplace accidents, today said it was aware of the incident and was making initial enquiries but may not launch a formal investigation.

Nobody was injured as a result of the collapse but a number of witnesses spoke of near misses and said they had been complaining for weeks about how demolition work was being carried out.

Tesco, which owns the land, is having it cleared to make way for a huge new housing development, including a 21 storey tower it wants to build there. A formal planning application is expected within the next month.

A spokesman from the demolition team working for Tesco today said: "During demolition of the building, two pre-cast wall panels fell.

"We are now working with the HSE (Health and Safety Executive) to understand the cause before recommencing works. We apologise for any inconvenience this has caused."

The HSE has since confirmed it is carrying out a full investigation and has issued the demolition firm GBM UK with a prohibition notice, ordering it to halt work on the building until improved safety measures are in place.