The FBI is scrambling to fill instructor positions and restart classes at its training academy after the lifting of a sequestration-forced hiring freeze that quieted the famed facility at Quantico, Va.

The bureau is short dozens of instructors who oversee a range of courses, as many were reassigned to other FBI offices when Congress imposed mandatory budget cuts. But with funding flowing again, the bureau wants to hire hundreds of special agents and analysts this fiscal year.

Owen D. Harris, the FBI’s assistant director of the training division, said he needs to fill about 40 instructor jobs in advance of the first new-agent class, which begins June 1.

The average class runs about 19 weeks, and Harris is planning to graduate about seven groups before the end of the fiscal year. By August, he said, about six overlapping classes will be in session. He is also anticipating that there will be six classes for new intelligence analysts.

“Of course it’s a heavy lift in an abbreviated time frame,” Harris said. “I am confident we will be ready to go when new-agent classes resume.”

Harris said most of the instruction at Quantico, which sits on 547 acres, came to a halt except for firearms training and other vital safety courses. The last class graduated in July, and since then, 285 agents have left the FBI, thinning the bureau’s ranks.

The FBI trains about 13,000 police officers from the United States and around the world each year, and those sessions, which were also interrupted by sequestration, will resume as well, Harris said.

Training and hiring are the “first two things that go,” said Harris, who noted that his budget was cut by about 50 percent when sequestration hit.

In an interview with reporters in September, FBI Director James B. Comey said he was stunned by the impact of the mandatory budget cuts. Because of forced reductions in spending, the FBI was not able to open important counterintelligence cases, he said. At the time, Comey said, the FBI faced $800 million in budget cuts.

Making sure that Harris has enough agents and analysts to train is the job of James L. Turgal Jr., assistant director of the human resources division. In an interview, Turgal said his division also had to endure steep cuts, losing about 100 employees. In 2010, there were approximately 70,000 special agent applications; only 900 were accepted.

Turgal also had to furlough more than 5,500 FBI employees for 20 days and offer early retirement packages to others. Currently, the FBI has 13,386 agents, with about 2,000 of them in the New York and Washington field offices.

The process of accepting candidates for new classes is time-consuming, and the bureau, he said, cannot simply snap its fingers and find recruits.

“It takes a huge machine to do that,” said Turgal, who previously was the special agent in charge in Phoenix and transferred to Quantico in February 2013. “I show up and the bottom fell out. The hiring stopped.”

All potential FBI employees have to undergo testing, interviews and lengthy background checks that include polygraphs. It normally takes about four months to complete the process. The quickest the FBI can do it, Turgal said, is about 60 days.

Before sequestration, Turgal said the FBI had cleared 337 people for hire. He said the FBI has remained in touch with them and all are still determined to join the bureau.

They “kept the faith,” he said.

Some will need their background checks refreshed, Turgal said, and all of them will be required to take new physical fitness exams.

Turgal said the FBI needs to hire 322 new agents and about 144 analysts to fill the new classes at Quantico.

So far, Turgal said, the FBI has 174 men and women scheduled to begin training.

“They’re all set to go,” he said. “The rest will be slower. We’ll get it.”