Toyota is launching one of its largest recalls on one of its most popular models—the Prius hybrid.

Covering all Toyota Prius and Prius Plug-in models built between June 2015 and May 2018, the recall involves a wiring harness for the car's hybrid power control unit, which can chafe and start a fire, the company told Reuters.

The problem surfaced in Japan, where one Prius began smoking, and led to the recall of more than 1 million cars worldwide, 192,000 of which are in the U.S. Affected models were sold in the U.S. as model years 2016-2018. Owners will begin receiving mailed notices this month.

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In addition to the Prius, the recall also affects Toyota C-HR plug-in hybrid models sold in Europe, Japan, and Australia, but not in the U.S.

Toyota said that where the wiring harness connects with the hybrid power control unit, the wires can contact the hybrid control unit's cover, and if dust accumulates on either the wire or the cover, vibration from driving can wear down the insulation on the wires and lead to a fire.

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At a little over 1 million cars, the recall is one of the largest in Toyota's history.

The Prius became a darling of environmentally conscious drivers before electric cars were widely available. The company has sold 4.3 million of the cars since they were introduced in 1998.

Now many Prius owners have begun to trade them for electric cars or plug-in hybrids, and the plug-in Prius Prime has become one of the leading plug-in hybrids in sales.