A segment of animated footage promoting the 2012 Olympics has been removed from the organisers' website after fears it could trigger epileptic seizures.
The logo was unveiled on Monday
Prof Graham Harding, who developed the test used to measure photo-sensitivity levels in TV material, said it should not be broadcast again.
Charity Epilepsy Action said it had received calls from people who had suffered fits after seeing it.
Organiser London 2012 said it will re-edit the film.
The new logo for the event, which is a jagged emblem based on the date 2012, was unveiled on Monday.
A London 2012 spokeswoman said the health concerns surrounded a piece of animation shown at the launch, which was recorded by broadcasters and put on the official website.
Emphasising that it was not the logo itself which was the focus of worries, she said: "This concerns a short piece of animation which we used as part of the logo launch event and not the actual logo."
She said the section of footage concerned showed a "diver diving into a pool which had a multi-colour ripple effect".
The spokeswoman said: "We are taking it very seriously and are looking into it as a matter of urgency."
Prof Harding is an expert in clinical neuro-physiology and he designed a test which all moving adverts need to undergo to check they will not trigger a reaction in people with epilepsy.
He told BBC London 94.9FM: "It fails the Harding FPA machine test which is the machine the television industry uses to test images.
"And so it does not comply with Ofcom guidelines and is in contravention of them."
Christopher Filmer rang BBC London 94.9FM to say he suffered a seizure while watching the footage on television and his girlfriend also suffered a fit and needed hospital treatment.
"The logo came up on TV and I was thinking about the 2012 Games and then I was out," he said.
Epilepsy Action said the images could affect the 23,000 people in the UK who have photosensitive epilepsy.
It said it had even triggered breakthrough seizures where people have a relapse after being seizure-free for a long time.
A spokesman for the charity said: "The brand incorporates both the Olympic and Paralympic Games, which is ironic as the latter is a showcase for athletes with disabilities.
"People can strive for years to gain seizure control and it is important that nothing puts this at risk."