SAN SALVADOR, El Salvador -- The Vatican is studying a possible miracle attributed to slain Archbishop Oscar Romero that could lead to the once-controversial cleric’s canonization, Roman Catholic authorities in El Salvador said Sunday.

San Salvador Archbishop Jose Luis Escobar Alas told reporters that church officials in the country are “convinced” of the miracle’s authenticity.

He cautioned that it could take a long time for the Congregation for the Causes of the Saints to consider the matter.

Romero is known to many as “Saint Romero of the Americas.” He was loved by the poor whom he defended and hated by conservatives who saw him as aligned with leftist causes ahead of El Salvador’s civil war.

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Romero was shot by a sniper in 1980 while celebrating Mass at a hospital chapel. A human rights campaigner, Romero had spoken out against repression by the Salvadoran army at the beginning of the country’s 1980-1992 civil war between the right-wing government and leftist rebels. His assassination presaged a conflict that killed nearly 75,000.

In February 2015, Pope Francis decreed Romero was killed out of hatred for his Catholic faith, approving a martyrdom declaration that set the stage for his beatification later in the year.