Learn German: Der Hersteller betont, er sage dazu nichts mehr. - The manufacturer emphasizes he is saying nothing more about it.

The verb sage is in the Konjunktiv I (Present Subjunctive) form. In German, this form is often used in news and formal writing to indicate reported speech. By using sage, the writer shows they are just reporting what the manufacturer claims, rather than stating it as a direct fact.

Can I use dass (that) in this sentence?

Yes, you could say Der Hersteller betont, dass er dazu nichts mehr sage. However, it is very common in German to drop dass when using reported speech. Notice that when you drop dass, the reported clause keeps normal main-clause word order with the verb in the second position (er sage), instead of kicking the verb to the very end.

What does dazu mean in this context?

dazu is a da-word combining da (it/that) and zu (to/about). The verb sagen often pairs with the preposition zu when talking about commenting on a topic. Instead of repeating the specific topic, we just use dazu to mean "about it" or "on this matter".

What is the difference between nichts mehr and nicht mehr here?

nichts mehr means "nothing more" or "not anything anymore", acting as the direct object of what he is saying. If the sentence used nicht mehr (not anymore), it would mean he is simply not talking at all anymore, rather than having nothing else to say about this specific topic.