PITTSBURG, Kan. (AP) — More than 1,000 Pittsburg State University students are unable to take laboratory classes so far this semester because of delays in a renovation project.

Crews have been working to replace heating, air-conditioning and exhaust systems at Heckert-Wells Hall. The project was supposed to be completed by Aug. 29.

University officials say Corvus, a subcontractor doing mechanical work, walked off the job the Friday of Labor Day weekend and never returned. Pittsburg State officials say it’s unclear why the workers left.

The Joplin Globe reports two mechanical contractors have taken over the project. It is now expected to be completed by Sept. 29. In response, faculty members are working to design their lab classes so the material is compressed into a shorter time frame.