HANGZHOU -- Authorities of an east China city Thursday ordered the demolition of poorly constructed homes, built by residents, after four of the frail structures collapsed earlier this week, killing 22.

Twenty-seven substandard structures near the site of the collapse in Lucheng, Wenzhou City, Zhejiang province, were earmarked to be demolished "as soon as possible," according to sources with Lucheng, which is engaged in a safety review of all buildings in the district.

This follows the collapse of four six-story buildings at dawn Monday. Twenty-two people were killed by the incident, while six survived.

The district government said that by late Wednesday, 278 families in Lucheng had been issued evacuation orders. District authorities say they plan to intensify efforts to crack down on illegal construction, usually built as residences or as rental properties for migrant factory workers around the area.

Lucheng district government claimed to have addressed safety issues in 7,234 homes this year and roughly 2,000 more homes will be checked by the end of this year.

Substandard homes are common in China's booming factory towns and cities under rapid industrialization. Lucheng is near Wenzhou, a costal city known for its vibrant business and entrepreneurship environment. Better job prospects have attracted migrants and business people to the city. According to a government census, Lucheng is home to 1.36 million people, 45 percent of whom are migrants.