Definately it is fungal contamination. Throw contaminated cultures away. Check other cointeiners whether contamination spreaded. Clean and sterilizise the incubator. Check also the medium bottle, whether it is contaminated. Sterilize the tips.
it looks like a sort of fungal contamination.If you have the stock of your cell,just start with the new one.for checking your media if it is contaminated or not,you just add the medium only to flask and placed in incubator.