The heart of a revered 19th century Argentine friar and patriot was stolen from an urn in the Franciscan monastery where it was kept for years as a religious relic, a church official said.

Whoever scooped up friar Mamerto Esquiu's heart on Tuesday left the urn it was stored in behind, said Jorge Martinez, head of the San Francisco monastery in the northwestern province of Catamarca.

"The theft was carried out because of the heart -- nothing else was stolen," he told local reporters. "It's very sad."

Witnesses reported seeing a bearded man run from the monastery around the time the heart went missing, but no one had been arrested, the Catamarca daily El Ancasti said.

Tuesday's theft marks the second time since 1990 that the friar's heart was mysteriously spirited away, the newspaper said.

Born in Catamarca in 1826, Esquiu entered the monastery at a young age and was ordained a Catholic priest in 1848. He gave stirring speeches and homilies supporting Argentine unity and its 1853 constitution, becoming a famed religious leader and patriot.

Esquiu died in 1883. When his body was exhumed for an autopsy shortly thereafter, church authorities said his heart showed no signs of decomposition. It was removed and given to the monastery where he had begun his religious studies.

Esquiu's body is entombed at a cathedral in the neighboring province of Cordoba.

Vatican authorities in recent years began to consider Esquiu for possible beatification, a step toward sainthood in the Roman Catholic Church.