BMW is recalling more than one million cars and SUVs in two recalls due to the risk of fires under the hood, and it's recommending that they be parked outdoors until repairs are made.

A spokesperson for the German automaker says the risk of fire is very low in both cases, but the vehicles should stay outside "in an abundance of caution." In both recalls, repairs are expected to start on Dec. 18.

The largest of the recalls covers over 740,000 328i, 328xi, 328i xDrive, 525i, 525xi, 528i, 528xi, 530i, 530xi, X3 3.0si, X3 xDrive30i, X5 xDrive30i, Z4 3.0i, Z4 3.0si and Z4 sDrive30i vehicles from 2007-11. Also included is the 2008-11 128i. All have six-cylinder engines.

Documents posted Friday by the U.S. National Highway Traffic Safety Administration show that a heater for the positive crankcase ventilation valve can overheat and cause the valve to melt, increasing the risk of a fire even when the vehicle is not in use. No injuries have been reported. Dealers will replace the heater.

The heater is designed to prevent the valve from freezing in cold temperatures, BMW spokesperson Hector Arellano-Belloc said. But irregularities in manufacturing can cause corrosion can lead to overheating.

The other recall covers nearly 673,000 cars including the 323i, 325i, 325xi, 328i, 328xi, 330i, 330xi, 335i, 335xi and M3 from the 2006-2011 model years. Also covered are the 2007-2011 328i xDrive, 335i xDrive and 335is, and the 2009-2011 335d.

Wiring for the heating and air-conditioning system can overheat and cause connectors to melt, also increasing the fire risk, even when vehicles are unattended. Four drivers reported injuries. BMW says a wiring connection can corrode and in rare cases cause fires.

Dealers will replace the wiring and connectors.

The recalls total about 1.4 million vehicles, but some are included in both, BMW said.

In total, about 15,000 vehicles are in Canada, a spokesperson told Reuters.