A Yale groundskeeper was seriously injured Wednesday when she was pinned against a wall by a lawn aerator while she was operating the machine in the Science Hill area.

Anna Lizasuain, a member of Yale’s grounds maintenance department, remained in critical condition in Yale-New Haven Hospital’s Intensive Care Unit on Wednesday night, a hospital official said.

Eric Uscinski, director of Facilities Operations, said he could not recall this type of accident ever having happened before with a lawn aerator.

“[Lizasuain] was operating the machine,” said Uscinski, who did not witness the incident. “She backed into a wall and was pinned against the wall.”

The accident occurred along Sachem Street in the area around Osborn Memorial Laboratories, Uscinski said. It occurred around noon, grounds maintenance supervisor Walter Debboli said, though he was not there when it happened.

A lawn aerator makes holes in the ground to reduce soil compaction without killing the grass. Reducing soil compaction allows water, oxygen and nutrients to reach the grass more easily. Debboli said Yale’s lawn aerator machines are hand-operated and can be anywhere from three to seven feet long.

Debboli said he believes Lizasuain has been a Yale employee for over 15 years. For the past four years, she has worked in the grounds maintenance department, grounds maintenance supervisor Walter Debboli said. Before that, Lizasuain was a member of the custodial staff, he said.

Under the contract between Yale and Local 35, Lizasuain’s union, she can receive sick leave pay for a total of approximately two and a half weeks’ worth of hours per year. If she is entitled to additional payments under Connecticut’s Worker’s Compensation Act, the sick leave pay would be incorporated into the total amount she receives.

John Bollier, the associate vice president for facilities operations, said that he did not have further details on Lizasuain’s condition, but that he would have more information Thursday morning.

“We’re all praying for her health,” he said.