An Australian university says the cutting down of more than 140 trees planted for a 13-year study destroyed its research and it's suing the contractor involved.

Maintenance workers at the University of Adelaide mistakenly chopped down the trees planted by researchers more than a decade ago as part of an effort to find a cure for a fatal tree disease, Britain's The Daily Telegraph reported Monday.

The trees had been planted to investigate Mundulla Yellows disease, which kills eucalyptus and has spread throughout Australia since the 1970s when it was first discovered in the South Australia town of Mundulla.

"When you have researchers that have put 13 years into a single experiment, to see the damage done in this way is absolutely devastating," Mike Brooks, the university's deputy vice chancellor for research, said.

The university, which is suing the contractor for $1 million, says maintenance workers sent to cut down excess woods in November ignored orders not to enter the research plot.

The contractor, while saying it was not responsible for the actions of its subcontractors, denied the school ever issued keep-out orders.

The university said two trees were cut down in 2008, resulting in an official order forbidding workers from entering the research plot unless accompanied by a university staff member.

In the recent incident, workers cut down 141 trees, damaged the trunks of five others and removed research metal tags showing the health of the trees, school officials said.