Loughborough MP Nicky Morgan says she "heard an almighty bang" and "saw clouds of thick black smoke" as the helicopter crashed into a crane in South London this morning.
The MP was walking towards Vauxhall tube station, when the accident happened.
"Ms Morgan says she "saw clouds and clouds of thick black smoke billowing from the ground" and that initial thoughts were that a bomb had exploded."
More top news
Remaining cloudy with outbreaks of showery rain this evening and tonight. Tomorrow will be a day of sunshine and scattered showers
Mainly cloudy with showers this evening. Tomorrow, mainly fine and dry at first before showers develop through the morning.
A man from Nottingham drowned during a holiday in Lanzarote when he attempted to save two swimmers in distress, an inquest has heard.