China's state news agency reports police have detained nine people in connection with the collapse last week of a cooling tower being built on a power plant site that killed 74 people.
Xinhua said the board chairman of the Hebei Yineng engineering firm was among those arrested.
China said last week 13 people had been detained. It was not immediately clear whether the nine suspects in Monday's announcement were part of that total.
The collapse of the tower in Jiangxi province prompted calls for better construction safety regulations and inspections.
China has vowed to improve its poor construction safety record, but anger over lax standards continues to grow.