July 31 (Reuters) - Drugmaker Amgen said on Friday hackers stole company data and patient health information in a cybersecurity breach involving cloud storage systems run by third-party providers.

On July 29, Amgen ( AMGN ) determined the incident was material, based on its evaluation of how many files appeared to be affected and the possibility that the information in those files could be sensitive, it said in a regulatory filing.

The company has activated its cybersecurity response plan, put containment measures in place, and brought in independent forensic experts to investigate.