Shares of Taser International, the US company that makes stun guns, have dropped 4.4% after US regulators stepped up an inquiry into the firm.
Taser has been criticised over the safety of its weapons and is facing a range of lawsuits from shareholders and families of Taser victims.
The company's stock has lost more than 80% of its value so far this year.
The Securities and Exchange Commission (SEC) has now expanded its inquiry, allowing it to seize documents.
The SEC had already opened an informal investigation into the company over the safety of its stun guns and the accounting for a distribution deal struck late in December 2004.
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