Earlier in the day, the 20 Minutos newspaper reported that an employee of the Ukrainian embassy in Madrid was slightly injured in the explosion of a device hidden in a mail envelope around 1:00 p.m. local time (12:00 GMT).
The employee was reportedly taken to a hospital. Ukrainian Ambassador to Spain Serhii Pohoreltsev later said it was a package with documents that exploded near the embassy rather than an envelope.
The newspaper cited Zaragoza police as saying that Instalaza received a package "similar in characteristics to the one sent to the Ukrainian embassy in Madrid."
Police said the package did not explode. The investigation is underway.
The report said that Instalaza manufactures grenade launchers that the Spanish authorities had sent to Kiev at the beginning of Russia's special military operation in Ukraine.
Spanish news agency EFE reported, citing sources, that the Spanish National Court was set to initiate trial proceedings after receiving a report on what happened from the police, with the judge considering the incident to be a terrorist offense since the package was addressed to Pohoreltsev.
Following the incident, Ukrainian Foreign Minister Dmitry Kuleba instructed his ministry to immediately strengthen the security of all Ukrainian embassies overseas.