The Virginia Tech building where a student killed 30 people and himself was reopened for limited use of engineering labs Monday, although access was restricted because of refurbishing work.

The closure of Norris Hall after the April 16 shooting rampage had stalled research by about 50 graduate students. About 10 of them were able to resume their work Monday, said Ishwar Puri, head of the engineering science and mechanics department.

Work in the three-story, 1960s-era building includes removal of asbestos from flooring. Puri said the main laboratory wing should be accessible in a week or two.

Officials decided to reopen the rest of the building because it contains sophisticated laboratory equipment that could not be moved.

Two security guards are posted at the building, and for now access is limited to daytime hours.

"This is a little inconvenient," Puri said. "Doctoral students work into the wee hours of the morning, particularly when they're working on research."

The second-floor classrooms where student gunman Seung-Hui Cho shot 25 students and five faculty members will not be used again.

The area of a separate dormitory where Cho shot two other students remains walled off.