ANGELES CITY (AP) – A nine-story building under construction here collapsed before dawn and at least 21 people were missing Sunday morning, authorities said.

Rescuers were “hearing voices” in the rubble, while 24 workers managed to dash to safety or were rescued, police and other officials said.

The building collapsed after a fierce thunderstorm in Angeles City in Pampanga province. More than 100 police and other government personnel were scrambling to rescue those believed to be trapped in the rubble, Police Regional Office-3 chief Police Brig. Gen. Jess Mendez said.

Mendez and other officials at the scene said there were no immediate reports of deaths but some of those who got out safely sustained injuries.

Among the 21 people who remained unaccounted for, most were believed to be workers at the building, according to Francis Pangilinan, who heads the Angeles City disaster mitigation office and was at the scene.

Two other people, including a Malaysian tourist, were injured when their lodgings were hit by debris from the collapsed building, officials said.

Rescuers, including firefighters, police, and disaster-response teams, used their hands and sniffer dogs in a dangerous scramble to search for the trapped survivors, Public Works and Highways Secretary Vince Dizon told reporters near the rubble of concrete slabs, twisted iron bars, and other debris.

“There are some signs of life...There are voices that are being heard,” Dizon said, adding that rescuers were moving with extreme caution. “It’s a very, very unstable site and the priority is to get the people out.”

Angeles City hosted one of the largest US Air Force bases outside of the American mainland until it closed in the early 1990s, helping develop Angeles and outlying cities and towns into entertainment and commercial hubs in Luzon.

The former air base, now called the Clark Freeport Zone, is about 80 kilometers (50 miles) north of Metro Manila.