Pope Francis was taken off mechanical ventilation and is stabilizing Tuesday following a pair of breathing crises, Vatican sources told Fox News.

The Vatican says that Pope Francis has suffered two new episodes of acute respiratory crises and has been put back on noninvasive mechanical ventilation.

ROME and LONDON -- Pope Francis suffered two episodes of "acute respiratory failure" on Monday, the Vatican said. The episodes were caused by a "significant accumulation of endobronchial mucus and consequent bronchospasm," the Vatican's press office said in a brief statement.