The U.S. Federal Aviation Administration and Boeing have privately issued notifications that the fuel switch locks on Boeing planes are safe, a document seen by Reuters showed and four sources with knowledge of the matter said.

The FAA and Boeing confirmed the safety of fuel switch locks on Boeing planes after a crash investigation raised concerns. Despite a previous advisory to check fuel switch locks, no mandates were issued.

The U.S. Federal Aviation Administration and Boeing ( NYSE: BA) have privately issued communications stating that the fuel control switch locks found on various Boeing aircraft, including the 787, don’t pose a safety risk, Reuters reported Sunday, citing document reviews and sources familiar with the matter.