Tā de dānxīn juéfēi kōngxué-láifēng, zhīqián quèshí yǒu guò lèisì shìjiàn.
His concern is certainly not without cause - there have been similar incidents before.
Tips
history
From Song Yu's Warring-States 《风赋》: 枳句来巢,空穴来风 - 'crooked branches invite birds to nest; hollow caves invite wind.' Classically it meant that an opening invites the relevant response - i.e. a rumor has a real cause behind it.
mistakes
Widely misused. Classical meaning: rumors have real basis (equivalent to 'where there's smoke, there's fire'). Modern popular usage often flips it to mean 'groundless rumor'. The PRC dictionary 《现代汉语词典》 now accepts both. To avoid ambiguity, pair with context: 并非空穴来风 (not without basis) is unambiguous.