Washington, D.C. ? The government is investigating whether popular acid reflux drugs Nexium and Prilosec cause heart problems, federal health officials said Thursday.

An initial analysis indicates the drugs don’t increase the risk for heart attack or other heart problems, and the millions of patients taking the medicines or doctors prescribing them should continue, Food and Drug Administration officials said.

AstraZeneca, the British maker of the two drugs, alerted the FDA of possible side effects May 29 after making a preliminary review of data from two small, long-term studies comparing the drugs’ effectiveness to surgery.

The FDA is reviewing more complete data from the two studies, as well as from 14 other studies examining Prilosec. Officials expect to finish their investigation in three months.