The head of the IAEA had warned the Seibersdorf facility was outdated
Pressure build-up at an ageing lab run by the UN's nuclear watchdog near Vienna has caused a plutonium leak.
Last year the head of the International Atomic Energy Agency (IAEA) warned the Seibersdorf facility was outdated and did not meet UN safety standards.
The leak happened in the high security area of the Seibersdorf site, 50km (31 miles) south of Vienna.
Austrian officials said the empty lab was sealed off and no-one was at risk. A full investigation is planned.
"Pressure build-up in a small sealed sample bottle in a storage safe resulted in plutonium contamination of a storage room... at the IAEA's Safeguards Analytical Laboratory in Seibersdorf," said the agency.
The lab is used to carry out tests on samples taken during IAEA inspection missions.
The IAEA said a full investigation would be conducted into the incident, which occurred in the early hours of Sunday morning.
The leak automatically set off an alarm via an air-monitoring system, said Daniel Kapp, a spokesman for Austria's environment ministry.
He added that radioactivity in the air would have been completely contained by the lab's filters, and Austrian monitoring centres had detected no increase in radioactivity, meaning no-one was in danger.
Last November, IAEA director general Mohammed ElBaradei said the site, constructed in 1970, did not meet UN safety standards.
He warned there was an "ever-growing risk" key components of the lab might break down, although the IAEA said there was no connection between Sunday's leak and the modernisation requirements.