Work at the Ranger uranium mine in the Northern Territory is resuming today, about six weeks earlier than expected.

Energy Resources of Australia (ERA) was forced to shut down processing operations in January, due to heavy rain during the wet season filling the tailings dam to near capacity.

ERA says the tailings dam water level has dropped from 53 metres to 52.7 metres, which is enough for production to start.

The mine is located near Jabiru, within the boundaries of Kakadu National Park.

In April, the miner said it expected operations at Ranger to be suspended until late July.

Workers have remained on site during the suspension carrying out maintenance and repairs.

ERA, which is 68.4 per cent owned by mining giant Rio Tinto, expects it will take about a month for the plant to reach normal production levels.

The company has revised its loss forecast for the first half of 2011 to between $20 million and $30 million, down from its previous forecast of $30 million to $50 million.

Share prices of ERA have fallen dramatically because of the mine closure.

At the close of stock exchange trade on Tuesday, ERA shares were at $4.04, down from just under $14 a year ago.

Earlier this month, environmental groups were warning Territorians to pay attention to a plan announced by ERA to expand its Ranger mine.

They say they believe the ultimate goal of the company is still to mine Jabiluka.

Jabiluka, also located within Kakadu, is the world's largest known undeveloped uranium deposit.

In the late 1990s, ERA won the right to mine the area.

But the traditional owners, the Mirrar people, opposed it and the mine shaft was filled in.

Australian Conservation Foundation (ACF) spokesman Dave Sweeney says ERA has its eyes on a bigger prize than just expanding its existing Ranger operations.

"It wants to stay active and in the region and wear people down, and wait for times to change," he said.

The Mirrar people are foregoing billions of dollars in royalties by opposing mining in Jabiluka, he says.

The ACF says ERA should abandon expansion plans at its Ranger uranium mine.