Rescuers in Bangkok are racing to find survivors in the rubble of an under-construction high-rise that came crashing down. At least 15 people have died in the collapse and more than 70 are missing.



Officials say when rescuers at the site asked for signs of survivors on Wednesday, they heard knocks from the rubble. Workers flew drones overhead to aid rescue efforts. Teams of specialists searched through the debris.



Authorities are investigating what caused the collapse. The building's construction was a joint venture between a Thai company and a Chinese state-owned firm. Thailand's industry ministry says some of the steel used in the building did not meet strength standards.
Officials say they will inspect other projects the Chinese firm is carrying out in the country.