The company today said that it started looking into the conduct of "a small number of individuals" in December. It says the investigation is ongoing.
On Monday the BBC reported that GlaxoSmithKline PLC is facing a bribery investigation in Poland, where a sales representative allegedly paid doctors to prescribe the company's asthma drug Seretide.
The company said it learned of the allegations in 2011 and found evidence of inappropriate communications by a single employee. It says that employee was reprimanded and disciplined.
The company is also facing a corruption investigation in China and is looking into alleged bribery in Iraq. Shares of GlaxoSmithKline rose 40 cents to USD 52.72 in midday trading.