Drugmakers are facing a US government investigation into paying bribes to boost their sales overseas, according to the Wall Street Journal.

The newspaper, citing people close to the matter, notes that a number of pharmaceutical giants, including Merck & Co, AstraZeneca, Bristol-Myers Squibb and GlaxoSmithKline, have in recent months disclosed they are being investigated for possible violations of the Foreign Corrupt Practices Act. That law makes it illegal for companies whose stock is traded across the Atlantic to bribe government officials in other countries.

The WSJ notes that the probe is being carried out by the US Justice Department and the Securities and Exchange Commission. It has sent out letters seen by the newspaper which  identified four types of possible violations: bribing government-employed doctors to purchase drugs; paying company sales agents commissions that are passed along to government doctors; paying hospital committees to approve drug purchases; and paying regulators to win drug approvals.

The investigation is focusing on Brazil, China, Germany, Italy, Poland, Russia and Saudi Arabia and so far, no company has been accused of wrongdoing.