Someone must have set it on fire.

文件着火了，肯定有人放火。

youdao

You may set metal pot on the fire, but you cannot set it on fire.

你可以把金属制的锅放在火上烧，但是你不能使它着火燃烧。

youdao

So I brought together all the dry wood I could get at hand, and making a good handsome pile, I set it on fire upon the Hill.

于是，我把附近的干柴通通收集起来，在山上堆成一大堆点起了火。

youdao

That's not enough to set it on fire, but it is enough to release the oil.

NPR: Industry Seeks to Extract Oil from Rocky Mountain Shale

Alexander Arredondo, had been killed by a sniper in Iraq, the distraught Arredondo smashed the windows of their van, climbed inside and set it on fire.

NPR: Marathon Rescuer Gets Attention From Press And FBI

His former partner Anna Lagwinowicz, 32, and uncle Tadevsz Dmytryszyn, 38, helped him put the body in a car and set it on fire, the jury was told.

BBC: Catherine Wells-Burr