The BBC has released a documentary about working conditions in Apple’s overseas production line, and Tim Cook’s not happy.

It was revealed in an email from Apple’s senior vice president of operations Jeff Williams to 5,000 retail employees in the UK that said he and Tim Cook were “deeply offended by the suggestion that Apple would break a promise to the workers in our supply chain or mislead our customers in any way.”

The documentary, which was in part put together with film taken by undercover reporters working on the assembly line details how poor living conditions, lack of breaks, and sleep deprivation is affecting the health of workers. It also shed light on how illegal tin could be entering the supply chain without the company’s knowledge.

In the email, Williams noted that “tens of thousands of artisanal miners are selling tin through many middlemen to the smelters who supply to component suppliers who sell to the world. The government is not addressing the issue, and there is widespread corruption in the undeveloped supply chain.

He went on to say that Apple could easily walk away and use suppliers from outside of Indonesia but that it would do nothing to improve the situation for Indonesian workers. ”We chose the second path,” he continues. “Which is to stay engaged and try to drive a collective solution.”

The documentary can be watched below.