June 13 (Reuters) - Boliden on Tuesday forecast a negative impact of 700 million Swedish crowns ($65.42 million) in the second quarter, owing to a production halt at its largest production unit, the Ronnskar smelter in Sweden.

The Swedish firm earlier said that a fire broke out overnight at the smelter, a major producer of copper, zinc, lead and other metals, and output from the site was halted until further notice.

"Due to stopped production at Rönnskär and lower grades than previously communicated at Kevitsa and Tara, EBIT during the second quarter will be affected by an estimated SEK -700 m," the company said in a statement.

Boliden provided a further update on the fire incident and said that plant's cell house was completely destroyed, while other production at Ronnskar had been stopped for safety reasons.

"The impact on EBIT is estimated at SEK -85 m per week during the time that all production is stopped," the company said, adding that it was still too soon to assess the depreciation in value of the destroyed buildings and equipment.

In a separate statement, the Swedish mining and smelting group temporarily halted production and exploration at its Irish Tara Mine, temporarily laying off its workforce effectively until conditions improve.

The company further explained that the Tara zinc mine, which employs about 650 people, is currently grappling with negative cash flow due to a variety of factors including operational issues, declining zinc prices, and high energy costs. ($1 = 10.6999 Swedish crowns) (Reporting by Akriti Sharma and Nilutpal Timsina in Bengaluru; Editing by David Gregorio)