Are the US government claims against ZTE and Huawei founded?

I’ve been reading a lot lately about Huawei being seemingly forced out of the US market due to fear of the devices being used to “spy on Americans and be used for undetected espionage.” However, I’m noticing that no one has made any technical information available, only citing ties to the Chinese government.

So my question is, are there any reasons why, from a technical standpoint, we should worry about these devices? Granted, since they manufacture their own microprocessors and several of their own components, I could see an argument for something being in the device or chipset that could be “suspicious”, but I honestly don’t know enough about hardware exploitation to know.

This is not meant to be a political post. I’m simply hoping to hear about some insights from people that have Huawei or ZTE hardware that they’ve had a chance to delve into. I soon will have an opportunity to play with one of these phones, and I would also appreciate any places to start looking.