LONDON (AP) — London firefighters combed through a burned-out public housing tower Thursday in a grim search for missing people as police and the prime minister launched investigations into the deadly inferno, with pressure building on officials to explain the disaster and assure that similar buildings around the country are safe.

At least 17 people were killed as flames raced through the 24-story Grenfell Tower early Wednesday, trapping people inside their apartments. Many people remained unaccounted for Thursday, and officials weren’t sure exactly how many were missing. But they expected the death toll to rise significantly.

London Police said a criminal investigation had been launched, and Prime Minister Theresa May announced a public inquiry, a type of probe that’s used to investigate issues of major public concern.

“People deserve answers. The inquiry will give them that,” said May, who set aside her efforts to form a new government Thursday to visit the scene of the blaze.

Residents of the huge Grenfell public housing complex, which had 120 apartments that housed as many as 600 people, said their warnings about possible fire risks had been ignored for years. The tower — in the working-class, multi-ethnic North Kensington neighborhood — is owned by the local government in the borough of Kensington and Chelsea.

Fire safety engineers were stunned at how rapidly the fire spread, engulfing the building in less than an hour in the middle of the night and preventing firefighters from reaching many people inside. Some jumped to their deaths rather than face the flames, and witnesses reported seeing small children thrown from the tower by their families in a desperate bid to survive.

Firefighters trying to race into the building were protected from the falling debris by police officers who placed riot shields over their heads.