The lawn aerator that seriously injured a University groundskeeper last week was a new model, and had been in operation for a total of only 20 hours, officials said Thursday.

Two separate investigations are being conducted into the accident that put Yale employee Ana Lizasuain in the Surgical Intensive Care Unit at Yale-New Haven Hospital. The reviews, one conducted by the University and the other by a federal safety agency, focus on the lawn aerator, though they are largely stalled until Lizasuain is well enough to talk about what happened before the accident. Pending the completion of the reviews, the aerator in question has been taken out of service.

Officials in the University’s safety office and the grounds maintenance department agreed to remove the $30,000 aerator from service until the internal review is complete, said Peter Reinhardt, director of the Office of Environmental Health and Safety. It apparently behaved differently than it would be expected to, he said.

The Toro aerator — a machine that makes holes in the ground to reduce soil compaction — first came to the University this fall, Grounds Maintenance Supervisor Walter Debboli said. A new model for Yale, it was one of four aerators on campus, aside from aerators used on University athletics fields.

“It was a state-of-the-art piece of equipment in that it is probably easier to maneuver overall, and its ability to aerify the soil is improved over the old ones,” he said.

Debboli said he thinks the aerator will eventually come back into service. Standard practice is to have a factory or sales representative demonstrate how to safely use a new piece of equipment when it is purchased, he said, and a Toro representative did visit when the machine arrived. Debboli said 20 hours is not a very short period of time for a machine to be in service, since it is only used for an hour or two each session.

Lizasuain, who has worked at Yale for 20 years, was pinned against a wall last Wednesday while using the hand-operated aerator. Key to Yale’s investigation, Reinhardt said, will be hearing Lizasuain’s firsthand account of how the machine was behaving before the accident. Though Lizasuain continues to improve, she is still unable to communicate what happened, he said. She remained in the Surgical Intensive Care Unit as of Thursday night in serious condition, a hospital official said.

Reinhardt said the Yale review is more broad than a separate investigation being conducted by the federal Office Safety and Health Administration.

“We’re looking globally,” he said. “We’re looking at how the University does aeration in general, if we should ever use [the aerator in question] again and, if so, how to do so as safely as possible.”

The OSHA investigation is centering on a possible equipment malfunction, according to Reinhardt, who said he spoke with an OSHA inspector assigned to the case. Citing agency policy, OSHA Area Director Robert Kowalski said he was unable to comment on the ongoing investigation. He said OSHA’s report will be completed within six months of the incident, as required by law, and will look to find the root cause of the accident.

Kowalski said the New Haven Fire Department — not Yale — informed OSHA about the accident, which is not an unusual step. While the federal administration is legally allowed on campus any time it wants, employers are required to call in OSHA only if the accident causes a fatality or causes more than three injuries requiring hospitalization, Kowalski said. He could not recall another recent OSHA investigation taking place at Yale.

But internal University safety investigations are not unusual, Reinhardt said. Any time there is an accident on campus it is investigated, even if it is something that would seem benign, such as a person slipping on a sidewalk, he said.

“Even in that case, we would see if there is a brick out of place, if the sidewalk needed repairs,” he said.