UPDATE 1-Star Cable, supplier to China's CNPC, says unable to contact top executives

HONG KONG, Sept 25 (Reuters) - The travails of companies working for oil giant PetroChina and its parent China National Petroleum Corp (CNPC) took another twist on Wednesday when one supplier said it had been unable to contact three executives, including its chairman, since they disappeared weeks ago.

Sichuan Star Cable Co Ltd also said another executive died this week. Caixin, an influential Chinese financial magazine, said He Yuying, 44, plunged to her death from a building in Chengdu, capital of Sichuan province, on Monday night.

The company, which mainly supplies cables to the oil and gas and power industries, first announced chairman Li Guangyuan’s disappearance on July 26. It did not give a reason but said it issued that statement in response to local media reports that Li was under official investigation.

Star Cable’s largest customer is CNPC, itself at the centre of a major graft investigation in which five former senior executives at CNPC and PetroChina are being probed.

A Star Cable official who only gave her surname as Yin told Reuters the company was still unable to reach Li, who is also the Shanghai-listed firm’s controlling shareholder.

Nor had the company been able to reach managing director Shen Ludong and chief financial officer Yang Ping since they disappeared late last month, Yin said from the firm’s headquarters in southwestern Sichuan province.

She declined to say whether the company was under investigation or not. The company was operating normally as it had appointed executives to fill both Shen and Yang’s positions, she added.

He Yuying was a board director and a deputy general manager in charge of sales, the company said. Yin said He’s family had notified the company about her death but did not provide a reason. He’s family could not be reached for comment.

The Caixin magazine gave no source for its report. A Chengdu police official told Reuters he was “aware of the death of He Yuying” but declined further comment.

One third of Star Cable’s first half revenue came from CNPC, according to its interim report for the period.

China’s government has said it is investigating the five former executives at CNPC and PetroChina, including a former chairman of both companies, for “serious discipline violations” - shorthand used to describe graft.

The investigation has sparked a sell-off in shares of mainland and Hong Kong-listed firms with close ties to PetroChina.

Hong Kong-listed Wison Engineering Services Co Ltd , a major PetroChina supplier, said last week that Chinese authorities investigating the company had seized records and temporarily frozen some of its bank accounts, adding it was no longer able to contact its chairman.

Wison had previously said chairman and founder Hua Bangsong had been assisting authorities in an unspecified investigation.

Shares of Star Cable, with a market value of about $390 million, closed down 2.77 percent on Wednesday versus a 0.41 percent fall in the broader Shanghai stock market.

The stock has fallen about 14 percent in the past year.

Star Cable was listed in Shanghai last year after raising about 762 million yuan ($124.49 million) from a domestic currency A-share offer.