Customs officers in the eastern Chinese city of Jinan confiscated 1,180 endangered butterfly specimens, the General Administration of Customs (GAC) announced Tuesday.

The specimens, among about 2,800 confiscated over the duration of the investigation, are under the protection of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

This is the largest confiscation of smuggled endangered butterflies since China joined CITES, according to GAC.

In early February, customs officers in Jinan, which is the capital of Shandong Province, found a suspicious parcel, which according to its declaration contained "skirts" from Malaysia. Upon inspection, 261 butterfly specimens were concealed inside.

Customs questioned a suspect, identified as Xu, and intercepted four more parcels addressed to Xu by March 7. The five parcels contained 829 butterfly specimens. More were found at the suspect's home and workplace.

The preliminary investigation indicates that since the beginning of 2015, the suspect had sourced the butterfly specimens online, with the intention to resell them at a profit. Customs had detained four suspects as of Tuesday.

CITES was launched in 1975 as an international agreement to address the global trade in specimens of wild animals and plants. China joined CITES in 1981.