Hundreds of giant Asian hornets were found in the invasive species' first known nest in the United States.

Officials said more than 500 "murder hornets" were found at the nest discovered in a tree last month in Blaine, Washington. A crew vacuumed out roughly 100 hornets after destroying the nest, but workers found hundreds more inside the tree the following week.

The crew had pumped carbon dioxide into the tree to kill any lingering hornets but discovered many were still alive upon looking inside. 

The nest was about 14 inches long and nine inches wide and had hornets in various life stages, including about 200 queens, an entomologist with the Washington State Department of Agriculture said.

"As far as we can tell, we got there just in time," entomologist Sven Spichiger said. "We know from the literature that a small percentage of these will go on to form colonies next year, should they have been given the chance to escape."

The findings from the Blaine nest come about a month after the first giant hornet was detected in the region. The agency placed live traps in the area in early October after a homeowner reported a specimen, Spichiger said.

Entomologist were able to capture a handful of hornets and placed trackers on them, one of which led to the hive which was located on private property. After observing dozens of hornets coming and going from the tree, the state got permission from the property owner to destroy the nest.