PERTH, Australia (AP) — Plugging a leak at an offshore drilling rig that has caused an oil slick off Australia will take weeks, the operator said Sunday, though officials said there was little threat of environmental damage.

Oil and gas have been leaking from a hole deep beneath the sea floor at the site of the rig between Australia's northwest coast and Indonesia since early Friday. Maritime authorities say the oil slick has been dissipating or evaporating fairly quickly.

The slick — measuring about 30 yards (meters) wide and nine miles (15 kilometers) long — is about 150 miles (250 kilometers) northwest of the Kimberley region. It was sprayed Sunday with a chemical dispersant by an Australian Maritime Safety Authority plane.

"There's no threat to the Australian coast," Resources Minister Martin Ferguson told Network Ten television. "It is evaporating naturally and the work of the Australian Maritime Safety Authority will merely assist in that evaporation."

Operator PTTEP Australasia evacuated 69 people from the rig on Friday as a precaution against fire breaking out from the condensate oil — a crude petroleum product used for blending — and gas leaking from the rupture about 1 1/2 miles (2.5 kilometers) beneath the sea floor.

No one was injured.

PTTEP chief financial officer Jose Martins said the depth of the leak made it hard to fix and difficult to determine its cause.

Martins said a mobile drilling rig had been ordered from Singapore and it would drill a well near the one that is leaking and install a pipe that could pump mud into the hole to plug it.

This could take up to seven weeks, Martins said.