What part of speech is the word "found" in the sentence below

A whale found dead on the southern Spanish coast was found to have swallowed 17 kg of plastic waste, including plastic bags.

I assumed it was a verb, as in a reduced passive form (a whale that was found dead), but the test said the correct answer was: "adjective"

Any ideas?

Solution 1:

It is a past participle in that sentence. A participle is internally a verb, in that it can have some arguments that verbs commonly have; externally, you could say it is an adjective, in that it often modifies a noun. But to call it merely "an adjective" without qualification seems excessively simplified, to the point where it becomes almost useless.

Solution 2:

It's a (passive) participle, a type of adjective derived from a verb. It's a participle syntactically, as well, because it can be rearranged like this:

Found dead, a whale on the southern Spanish coast was found to have swallowed 17 kg of plastic waste, including plastic  bags.

It is still an adjective relating to the noun, but the placement is more free. Although that might, depending on the reader, have a very slightly different semantic meaning, as it no longer absolutely must be related to the whale. Although otherwise would be confusing.