A routine pool cleaning triggered an explosion at a resort in the Philippines, leaving at least 19 people hospitalised.

The chemical reaction occurred after a bucket containing muriatic acid was mistakenly added to a chlorine-treated swimming pool at Alcoseba's Resort Hotel in Talisay City, Cebu.

Footage shows a maintenance worker carrying out cleaning duties near the water when the pool suddenly erupted on Tuesday evening, September 2.

Caretaker Lita Diaz said one of their workers had been cleaning the facility and believed he was pouring chlorine into the water. However, an internal investigation by the management later confirmed the bucket actually contained muriatic acid.

Diaz added: 'We usually use small amounts of muriatic acid. We don't mix it together with chlorine and alum at the same time. We add them separately, one by one.'

Emergency crews arrived at the scene shortly after several individuals reported nausea and vomiting.

Nineteen people, including the maintenance worker, who sustained burns to his face and body, were taken to the hospital for treatment.

Alvin Santillana, head of Talisay City Disaster Risk Reduction and Management Office, said: 'Based on the CCTV footage, there were bursts when the chemical was poured into the water. That reaction was caused by the muriatic acid coming into contact with the chlorinated pool.'

Officials have issued a cease-and-desist order, suspending the resort's operations while an investigation is underway.

Chlorine is commonly used in pools as a disinfectant to kill bacteria and keep the water safe for swimming. Muriatic acid, a diluted form of hydrochloric acid, is often used in small amounts to adjust the water's acidity or remove mineral deposits. However, the two chemicals must never be mixed directly, as the combination can produce hazardous fumes or trigger explosive reactions.