Following up on yesterday’s story in which some iPhone 4 users are experiencing slow upload speeds on AT&T’s network, the incident may be a genuine bug and not intentional data capping.

Per AppleInsider, users across the U.S. have reported upload speeds of around 100Kbps, well below the capabilities of the HSPA-capable iPhone 4. The issue has affected users in a number of major metropolitan areas across the country, including New York and Los Angeles.

While some speculated the problems were a result of bandwidth throttling by AT&T, that is not said to be the case. Instead, sources close to the story have stated that the issues are a result of an unintentional software glitch related to High-Speed Uplink Packet Access in some sections of the country. When working properly, HSUPA can allow uplink speeds of 5.76Mbit/s.

It is believed that a fix for the issue is forthcoming, though AT&T did not provide a comment on the matter as of Tuesday evening.