Iraq’s Health Ministry said 621 Shiite pilgrims suffered respiratory distress after inhaling chlorine from a leak at a water-treatment facility on the Najaf-Karbala route overnight Saturday. The gas spread as worshippers travelled toward Karbala for Arbaeen, one of the world’s largest annual religious gatherings. All of the affected pilgrims received treatment for asphyxia and were discharged in “good health,” the ministry said on Sunday. Security forces protecting the procession attributed the incident to a malfunction at the station, which sits along the main corridor linking the two holy cities. The episode underscores chronic weaknesses in Iraq’s public-service infrastructure after decades of conflict and under-investment. Millions of faithful are expected to converge on Karbala in coming weeks to mark the 40-day mourning period for Imam Hussein, heightening pressure on health and safety systems along the pilgrimage route.