Austria's financial markets watchdog FMA is investigating AMS' top management on suspicion of illegal share transactions during the ongoing takeover of Osram, a spokesman said on Thursday.
"As a matter of principal we investigate any indication of a violation of law," the FMA spokesman said, adding that the authority was reacting in response to several reports. He did not provide details.
The Swiss and the German finance watchdogs are supporting the Austrian authority's investigation into suspected market manipulation and insider trading, German daily Handelsblatt said.
The paper earlier reported the probe, triggering a 16% drop in AMS shares.
"AMS is not aware of any investigation or similar case against any board member or employee of AMS," the Austrian company said in a statement. "AMS is also not aware of any related requests by authorities."
Switzerland's watchdog FINMA does not comment on specific investigations but "always takes a close look at conspicuous transactions and transaction volumes", a spokesman said.
A spokeswoman for Germany's Bafin did not have an immediate comment.
(Reporting by Kirsti Knolle; Additional reporting by Silke Koltrowitz in Zurich, Hans Seidenstuecker in Frankfurt; Editing by Jan Harvey)
