The phrase "authorities grew" is correct and usable in written English.
It can be used to describe an increase in power, influence, or presence of authorities over time or in a specific context.
Example: "As the situation escalated, the authorities grew more vigilant in their response to the crisis."
Alternatives: "authorities expanded" or "authorities increased".
He was arrested on Aug. 16 in Minnesota after the authorities grew suspicious of his conduct.
The authorities grew concerned that Mr. Hopler, who lost his eyesight because of diabetes, could not safely maintain his collection.
As international condemnation of the authorities grew, some diplomats said Western aid to Tanzania could be affected.
The Chinese authorities grew more alarmed in 2009, after a proposed joint venture between Rio Tinto and BHP Billiton threatened to give the mining giants extraordinary power over the price of iron ore, a vital ingredient in making steel.
According to the report, Libi later told the C.I.A. that the Egyptian authorities grew dissatisfied with his level of cooperation, so they locked him in a tiny cage for eighty hours.
You could see how his scepticism towards the German authorities grew as he complained more and more about the militarism of the Games and about how there were far too many uniforms about for his liking.
Baidu's domestic legal setbacks have been interpreted as reflecting the Chinese authorities' growing intolerance of copyright infringement.
In another sign of the authorities' growing concern, state media on Monday reported that a senior monk from a Sichuan-based organisation had described the self-immolations as a form of extremism that degraded Buddhism, adding that they had triggered "public bewilderment and repulsion".
The companies mostly began as local businesses bidding for space from local airport authorities, growing with the industry and never seeing a benefit from going public.
While studies of the effect of pegvisomant on surrogate outcomes such as the IGF1 level are numerous, the impact of this GH receptor antagonist on comorbidities of acromegaly is poorly documented, despite health authorities' growing demands for hard endpoints.
His attacks on political authority grew sharper, more persistent, more amplified.
