Spain's Tourism Minister Reyes Maroto has received a knife covered in red stains by post, an interior ministry source said on Monday, days after senior security officials and the leader of the Unidas Podemos party were sent death threats.
An investigation has been opened, the source said, without providing more details.
A separate source from Maroto's ministry said it was unclear whether the red stains on the knife were blood or paint.
Maroto, a socialist, has served as minister of industry, trade and tourism in Spain's left-wing government since 2018.
Last week, Interior Minister Fernando Grande-Marlaska, Pablo Iglesias of the far-left Unidas Podemos party and Maria Gamez, who heads the Guardia Civil police force, also received death threats in the mail.
"Your wife, your parents and you are sentenced to capital punishment, your time is running out," said the letter to Iglesias, a former deputy prime minister.
He posted the letter on Twitter along with a picture of four bullets that he said came in the envelope.