MEXICO CITY (AP) — Torrential rains in central Mexico suddenly flooded a hospital early Tuesday, killing 16 patients, possibly due to the loss of oxygen equipment as the power went out, the national Social Security Institute said.

A video posted on the agency’s social media feed said that about 40 other patients survived as waters rose suddenly in downtown Tula and flooded the public hospital around 6 a.m.

Video recorded inside the hospital showed knee-deep water as staff frantically tried to move patients.

Hidalgo state Gov. Omar Fayad said earlier that 10 had died in Tula, about 60 miles (100 kilometers) north of Mexico City.

IMSS Director Zoé Robledo said the waters knocked out power to the area as well as the hospital’s generators.

He said the hospital had been caring for 56 patients, about half of them suffering from COVID-19.

Tula Mayor Manuel Hernández Badillo said in a news conference that rescue teams were working in the city. “Today the important thing is saving lives,” Hernández said.