Can the IR filter be removed from iPhone 3G and earlier?

I really would like to modify an early generation iPhone (1st gen/3G/3GS) to be able to capture IR images. From the research that I have done, it looks like the IR filter is mounted directly to the CMOS sensor on iPhone 4 and subsequent models. Ideally, I’d like to know if the IR filter in the iPhone 3G or 3GS is part of the lens housing, or if it’s fixed directly to the CMOS sensor. I would appreciate any insight/help that anyone could provide.