Security at the Forsyth Barr Stadium building site in Dunedin has been stepped up after intruders tampered with machinery earlier this month.
Police have so far not identified those who broke into the site and drove a crane, attached to a roof truss, more than 20m early on October 3.
Fingerprints had been lifted from the crane but police were still waiting for a search of the fingerprint database to be completed, Sergeant Tony Ritchie, of the Dunedin police intelligence unit, said.
The crane had been hooked to a roof truss but whoever moved it about 4am slackened the line and the truss was not damaged.
Earlier the same night, someone crashed a scissor lifter into another scissor lifter on the fourth floor of the unfinished south stand, where walls were also damaged.
Carisbrook Stadium Trust chairman Malcolm Farry said contractors had improved their security procedures after the incidents.
Contractors checked the way buildings and machinery were secured when workers left the site for the evening, and those procedures had since changed.
Asked whether those procedures included removing keys or starter mechanisms from the cranes and locking their doors, Mr Farry said all aspects of the lock-up were being looked at.
A report on the incident from the project manager did not mention whether the crane was locked, nor whether keys might have been left inside, Mr Farry said, when asked.
"No doubt" that possibility was part of the investigation, he said.
