A mother and her son who were trapped under the collapsed quarantine hotel in Quanzhou City, southeast China's Fujian Province for nearly 52 hours were rescued on Monday evening.

They were first discovered by the life detector device at around 6 p.m. and local firefighters further confirmed their accurate position by knocking and shouting.

However, it's not easy to pull them out of the rubble. To avoid secondary injuries, rescuers could only use manual equipment and bare hands to clear up the obstacles, including wooden boards, bricks and steel bars, to open a rescue channel.

Firefighters can only work in single line, kneeling or lying down in the clearing work.

After nearly three hours' effort, the mother and her 10-year-old son were successfully pulled from the rubble at around 11 p.m. They were sent to a local hospital for treatment.

The mother told firefighters that another person aged around 20 was trapped under the rubble.

At least 20 people were killed when Xinjia Hotel collapsed on Saturday, local media reported. As many as 61 people have been rescued, and 10 people are still trapped under the rubble.

The hotel had been transformed into a quarantine facility for those who had close contact with confirmed COVID-19 patients, according to media reports.

Until Monday evening, the Ministry of Emergency Management had ordered local fire and rescue corps to deploy nine teams with a total of 853 rescuers, 47 sets of life detectors, nine search and rescue dogs and other equipment.

Local authorities have launched an investigation and the owner of the building is being held in police custody.

Shang Yong, Vice Minister of China's Ministry of Emergency Management, said at a press conference on Tuesday that the collapse was caused by illegal construction work and repeated illegal reconstructions at the hotel.

He added that the accident revealed loopholes and blind spots in local safety rules and the lack of fulfillment of responsibilities by local authorities.