The Taiwanese phone maker HTC slumped 6.9 per cent to NT$225 in Taipei yesterday following the announcement that the exchange was looking into unusual trading before Sunday's patent deal with Apple.
Michael Lin, a spokesman for the stock exchange, said the inquiry was standard procedure and "[not] necessarily related to insider trading". He said the disclosure of the Apple settlement would be taken into account.
HTC climbed 6.9 per cent on Friday as 26.7 million shares changed hands, more than double its daily average this year.
On Sunday it was announced that Apple had settled all global lawsuits with HTC, whose smartphones use Google's Android operating system. Apple had accused HTC of copying features that made its iPhone unique.
For its part, HTC claimed Apple had infringed wireless patents. HTC is the maker of the One, Desire and Sensation handsets.
The companies said they had signed a 10-year licensing deal, but declined to provide details.
Shaw Wu, an analyst at Sterne Agee & Leach, suggested in a research report yesterday that Apple would probably receive US$6 to $8 per phone, or $180 million to $280m a year from HTC.
HTC's share of the global smartphone market fell to 5.8 per cent in the second quarter from a peak of 10.7 per cent a year earlier, according to Bloomberg Industries data.
Apple was second with 16.7 per cent. The deal signals a new willingness by the company to resolve patent disputes without resorting to the "thermonuclear war" stance favoured by its late founder Steve Jobs.
Mr Wu said the accord might also serve as a blueprint for Apple to resolve patent disputes with Samsung and Google's Motorola Mobility business.