French health regulator ANSM has launched a probe into the drug Diane-35, used to treat acne and also as a contraceptive, after linking it to four deaths over the past 25 years.

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Produced by the German drugmaker Bayer, Diane-35 is authorized in 135 countries and sold in 116.

In 2012, about 315,000 women in France used the drug, ANSM said in a statement on Sunday.

Four deaths due to thrombosis – a kind of blood clot – were linked to the use of Diane-35, ANSM said, promising to release a full report on the drug and its risks next week.

Three other deaths reported by French newspaper Le Figaro on its website as connected to the drug were linked to existing health conditions, the regulator confirmed.

Diane-35, also sold as Dianette in some countries, is a hormone tablet that treats certain types of acne for women and is also used as a contraceptive.

A database of information from French doctors shows 125 cases of thrombosis related to Diane-35 or other forms of the drug since 1987, when the drug was first released onto the market.

In response, Bayer said on Sunday that the blood clot risk was "known and clearly indicated in the patient information leaflet".

Bayer added that the drug was only supposed to be prescribed for acne, and in the context of a medical consultation addressing all the precautions of use.

In France, Diane-35 is only authorized for the treatment of acne, but its hormone make-up means it could work as a contraceptive by blocking ovulation.

France announced last year that so-called third generation birth-control pills – newer pills that contain variants of the hormone progestin – will no longer be reimbursed by the social security system from March.

Earlier this month, ANSM launched a probe into the use of newer contraceptive pills on the market over fears of blood clots after a woman sued Bayer over an alleged clot caused by her pill.

One French lawyer told French media on Sunday that around 100 women had contacted him, intending to sue both Bayer and ANSM for not raising the alarm sooner.