Sharp Corp., Japan's top manufacturer of liquid crystal display panels, expressed surprise Wednesday at news of a global price-fixing probe but pledged its full cooperation, as did a clutch of rival firms also under investigation.

Competition authorities in Japan, South Korea, the European Union and the United States have launched a joint investigation into suspected anti-competitive activities by the flat panel makers, officials said Tuesday.

"We are at the very beginning of the investigation so we don't know yet if all of these companies have committed illegal activities," said Akinori Yamada, an official at Japan's Fair Trade Commission.

In Japan, Sharp Corp., Seiko Epson Corp., Toshiba Matsushita Display Technology Co. and NEC LCD Technologies Ltd. confirmed that they were among the companies under investigation, as did Samsung Electronics in South Korea.

"Honestly, we are surprised at the investigation, as we have been doing our business openly and squarely," said Sharp spokeswoman Miyuki Nakayama.

"It's unthinkable to us that cartel activity took place given the fact that prices of LCDs are dropping sharply in the market," she added.

Seiko Epson, a specialist maker of small-sized LCDs for mobile phone handsets, said it was also under investigation along with its joint venture with Sanyo Electric.

"We will cooperate with authorities but most of our products are custom-made for makers of mobile phone handsets, which don't suit cartel (activities) in general," said a spokesman for Seiko Epson.

Toshiba Matsushita Display Technology, a joint venture between Toshiba Corp. and Matsushita Electric Industrial Co., said it had been ordered to submit a report to the Japanese authorities but declined to comment further.

In Seoul, a Samsung Electronics spokeswoman said its US and Japanese subsidiaries had also been served with subpoenas but stressed the company was "strongly committed to fair competition".

The London-based Financial Times, quoting an unnamed industry executive, reported that regulators are examining possible price fixing of LCD panels in 2003 and 2004 when the industry was enjoying an upturn.

Japan's Nihon Keizai business daily meanwhile cited anonymous sources as saying the alleged collusion was an apparent bid to reduce output to prevent a plunge in LCD panel prices.