* Chinese regulator not saying why Qualcomm investigated
* China key growth market for Qualcomm
* Qualcomm shares fall 2.6 pct
Nov 25 (Reuters) - Qualcomm Inc said China's price regulator has started an investigation of the mobile chipmaker under the Chinese Anti-Monopoly Law, sending the U.S. company's shares down 2.6 percent.
Qualcomm said it was not aware of any violation but would cooperate with the investigation by China's National Development and Reform Commission (NDRC).
Qualcomm, the world's biggest maker of cellphone chips, gets half of its revenue from China and has sought more growth there as telecom operators such as China Mobile upgrade their high-speed network services.
The NDRC did not say why Qualcomm was being investigated. However, Evercore Partners analyst Mark McKechnie said the investigation seemed to be part of a wider probe into the industry and not specific to the company.
Qualcomm also sells chips and licenses technology to Chinese companies looking to export their devices into overseas markets.
Its revenue from China rose 54 percent to $12.3 billion this year, 49 percent of total revenue.
Qualcomm did not immediately return calls seeking further comment.
"It is a little bit inauspicious because it corresponds with seemingly some confirmation that the Chinese government will be granting new spectrum licenses to allow for the launching of LTE (high-speed 4G networks) in China in the middle of December," Pacific Crest Securities analyst James Faucette told Reuters.
China's state media quoted on Sunday an NDRC official saying the country will focus antitrust investigations on six industries, ranging from technology to medicine.
The Chinese government is probably trying to push for local technology suppliers, McKechnie said.
In the last few months, organizations affiliated to the Chinese government spent nearly $3 billion to buy Chinese mobile chipmakers Spreadtrum Communications Inc and RDA Microelectronics Inc.
With growth in the smartphone industry shifting away from wealthy markets toward China and other emerging economies, Qualcomm has focused on supplying chips for cheaper phones, in competition with Chinese rivals such as Spreadtrum.
China Mobile Ltd, the world's biggest mobile company with 800 million subscribers, is investing billions of dollars to upgrade its infrastructure so clients can enjoy speedier Internet and data access once the government awards 4G telecom licences.
The NDRC is China's top economic planning body and regulates prices. It has launched nearly 20 pricing-related probes into domestic and foreign firms in the last three years, according to official media reports and research published by law firms.
The NDRC fined six companies, including Mead Johnson Nutrition Co, Danone SA and New Zealand dairy giant Fonterra, in August following a four-month investigation into price fixing and anti-competitive practices by foreign baby formula makers.
China had put pressure on around 30 foreign firms, including General Electric and Siemens, to confess to antitrust violations and warned them against using external lawyers to fight accusations from regulators, Reuters reported in August, citing sources.
Qualcomm shares were trading at $71.06 in morning trade on the Nasdaq on Monday.
Infrastructure spending on 4G will nearly triple to $24.3 billion in 2013 from $8.7 billion in 2012, according to research firm IHS iSuppli, fueled by network expansions in major markets such as China, Japan and Germany.