Just days after the Senate Commerce Committee chairman demanded additional information from Apple regarding slowing down older iPhones, four additional U.S. House Republicans have also sent a letter to Apple CEO Tim Cook concerning the issue…

As reported by Reuters, among those who signed the letter is Greg Walden, chair of the House Energy and Commerce Committee. While the specific content of the letter is not disclosed, it is targeted towards Tim Cook and seeks information about the “disclosure” that Apple “slowed older iPhone with flagging batteries.”

Furthermore, the letter is said to raise concern regarding an evacuation at a Swiss Apple Store earlier this week. As we reported at the time, the store was temporarily evacuated and emergency services were called to the scene after smoke was emitted from an overheating battery.

Since Apple announced its discounted battery replacement program, we’ve heard reports of at least two iPhone battery explosions. In addition to the one in Switzerland, we also reported on one in Spain earlier this week. The cause of both instances, however, remains unclear.

Apple regularly comes under scrutiny by lawmakers due to its extensive size and power in the technology industry, so it shouldn’t come as too big of a surprise to see questioning concerning the iPhone slowdown situation. Ultimately, however, it’s unlikely that Apple will offer any additional information in response to these requests.

We’ll update if the full letter is made available, as well as if Apple formally responds to the request for additional information.