“It’s a little bit tricky because this species makes their nest under the ground — more than 30 meters — so it is not easy to find,” he said. “We are trying.”

30 meters seems kind of unlikely to me. 30 centimeters, maybe?

kagis

https://www.orkincanada.ca/blog/the-asian-giant-hornet-murder-hornet-what-you-need-to-know/

Unlike other species of Vespa, V. mandarinia  Asian Giant Hornet prefers to nest underground. With rotten pine roots being a common nesting material for these hornets, however, snake or rodent tunnels that have already been dug up  have also been used to nest.  The depth of these nests are between 6 and 60 centimetres (2.4 and 23.6 in).

Yeah, that seems more like the right range.