Geico came to Katy in 2013 with about 20 employees and plans to grow rapidly. As the insurance giant gets set to celebrate the one-year anniversary of its West Houston headquarters along I-10, hundreds of more invitations to the office party might need to be sent to new employees.

Geico officials have announced they will add more the 300 jobs at its claims operation center at Mason Creek Corporate Park near the Grand Parkway. Interviews have already begun, officials said.

"It's simply so exciting to be here in the Katy area with the growth," said Tara Carthew, general manager of the Katy office. "I was just interviewing somebody who moved back here and they were amazed at the changes. I'm always seeing new buildings pop up. It's great to be at a company that's part of that here."

The 300-plus jobs coming to the Katy office will be entry-level and management development program positions with annual salaries ranging from the mid-$30,000s to the $40,000s, Carthew said.

Geico's Katy office has seen massive growth in its first year.

Carthew said that about 15 percent of the Katy staff transferred from within Geico to supervise and train new employees. The rest of the staff has been new hires, mostly from the Houston area.

About 20 associates began working in Katy after the Dec. 2, 2013, opening, and about 50 employees from a nearby Geico office joined the group. A hiring blitz then brought in hundreds of more workers, Carthew said.

"We received more than 10,000 applications after our ribbon-cutting," she said.

Today, about 540 full-time employees work in Katy at the 135,000-square-foot building, Carthew said.

Renovations within the building's shell to house the incoming wave employees will complete Phase 2 of the site's build-out and take up all available office space, she said.

"When we initially came here, we had some aggressive hiring goals and we met them and exceeded them, but not by much," Carthew said. "I don't think we were supposed to occupy the rest of the building until the middle of next year, but we'll now be doing that by the end of the first quarter."