Updated 4:46 p.m.
The tallest building in Philly is officially open for business.
Four years after construction was first announced on the Comcast Technology Center at 18th and Arch, employees are moving in.
The first round of people moved into the building on Monday morning, a source close to Comcast confirmed to Billy Penn, and even more employees will continue to relocate there gradually for the next several months.
Around lunchtime on Monday, employees were seen entering and exiting the building. Several of them needed some help from security guards to get in — the swipe card access on the outside of the building is an adjustment from the swipe card access inside the building near the elevators at the first Comcast Center.

Construction workers were also seen using handcarts to move boxes from the back of the first Comcast Center into the Comcast Technology Center.
According to a security guard working there, the new building isn’t yet open to the public.