Unfortunately, the content of the letter was not disclosed, but what is certain is that it was written exclusively to Cook and hopes the latter will disclose more about Apple's slowdowniPhoneInformation on speed.
In addition, the letter also mentioned the incident occurred in Switzerland due to overheating of the iPhone battery, and lawmakers are worried that such a situation may happen again.
Since Apple announced the battery replacement project, so far have heard at least two iPhone bombings. Similar events have taken place in Spain except Switzerland. However, the specific reasons behind are still hard to say.
Due to its size and strength, Apple is often censored by lawmakers, and not surprising at the latest. However, it seems unlikely that Apple will eventually provide additional information on these requirements.