Sprint has switched on its 4G LTE network in some pockets of San Francisco, New York City (and other parts of New York State), Washington, DC and some "cities in Florida," including Jacksonville, Miami and Tampa, as spokesperson Kelly Schlageter told The Verge via email on Monday. Sprint began turning on 4G LTE in San Francisco about a month ago, but coverage across the city remains spotty for now, as Engadget observed when testing devices on a drive through the city.

"Deployment is just beginning in San Francisco," Schlageter wrote. "Coverage area is somewhat hard to describe at this stage because sites generally aren't contiguous. There are sites on air in and around SF, kind of like popcorn."

"There are sites on air in and around SF, kind of like popcorn."

The new pockets of service come in addition to the 58 areas that Sprint announced in its latest coverage update in late January. Sprint is holding off on making an official announcement of 4G LTE coverage until its infrastructure is built up enough that it can provide steady, continuous service, or as the Schlageter put it, until Sprint achieves "a density of sites to indicate that our customers should consistently have a great 4G LTE experience."

Sprint said that this approach was designed to let customers have access to the service in a few sporadic test areas before the company makes official launch announcements.

"Rather than deploy a site, test the equipment and then turn it off until we launch, we are leaving the sites on and customers are welcome to use the Sprint 4G LTE network wherever they find it," Schlageter told The Verge.

Customers can check specific coverage in their own regions using maps on Sprint's website. The company said in its latest earnings call that it was slightly behind in its initial target of near-nationwide 4G LTE rollout by the end of 2013, but is on track to hit areas covering 250 million people by early 2014.