Chris Yates, an aviation security expert, told CNN it was likely there would be questions about whether the helicopter should have been flying in these conditions.
Under safety regulations, tall buildings must have navigation lights on top to make them apparent to low flying aircraft, he said.
Helicopters are not supposed to fly within 500 feet of tall structures in central London, he said.
The London Heliport is nearby on the banks of the Thames, at Battersea.
The incident caused major disruption for many people on their way to work.
Vauxhall, with a rail station, Underground station and large bus station is an important transit point for those traveling from the south to other parts of London.
The Vauxhall area has been earmarked as a major development site.