(Reuters) - The U.S. Food and Drug Administration said on Tuesday it has stopped all pediatric clinical trials of Amgen Inc's Sensipar after the death of a 14-year-old patient taking part in a study of the drug.

Sensipar, which is approved for adults, is used to lower dangerously high calcium levels in the blood.

The agency said it was collecting information on the circumstances of the teenager's death. It said it does not know if the Amgen drug had any role in the death.

"This communication is intended to inform health care professionals that we are evaluating the information and will communicate our final conclusions and recommendations when our review is complete," the FDA said in a statement posted on its website.

Amgen, the world's largest biotechnology company, said it had sent a letter last week to healthcare providers alerting them to the trials' halt and the patient death.

"Amgen is working as rapidly as possible to understand the circumstances of what happened. This analysis is ongoing and will be concluded as quickly as possible," the company said in a statement.

Sensipar works by decreasing the release of parathyroid hormone from the parathyroid gland to lower calcium levels in the blood. High levels of calcium in the blood can lead to serious health problems.

Sensipar, which had worldwide sales of $950 million in 2012, is approved to treat adults 18 and over. The trials were being conducted to determine the safety and efficacy of the drug in younger patients.

Drugmakers also often conduct pediatric trials because they are rewarded with an additional six months of patent protection for testing medicines in children.