The European Union’s drugs regulator has asked pharma companies including Novo Nordisk A/S and Eli Lilly & Co. for more information as it reviews the potential risk of suicidal thoughts associated with a new class of weight-loss medicines.

The European Medicines Agency started investigating the issue in July after reports of suicidal thoughts and self-harm from people who had been taking the anti-obesity drugs. The review is focused on so-called GLP-1 treatments, a class that includes Novo’s Wegovy weight-loss shot as well as its diabetes medicine Ozempic. The drugs are among the hottest sellers in pharma.

Read More: EU Widens Probe of Suicide Risks Linked to Weight-Loss Drugs

In a statement Friday, the EMA’s safety committee said it had reviewed all clinical trial evidence and published literature on the subject, adding: “While at this point no conclusion can be drawn on a causal association, there are several issues that still need to be clarified.”

The committee has agreed further lists of questions to be addressed by the makers of these medicines and said it will discuss the topic again at its meeting in April.

Though their use for weight loss is comparatively recent, GLP-1 drugs have a more than 15-year history as treatments for diabetes. The EMA investigation also includes dulaglutide, the active ingredient in Lilly’s diabetes medicine Trulicity, and AstraZeneca Plc’s diabetes drug Byetta.

--With assistance from April Roach.