Authorities in Shanghai said late Tuesday they are investigating the identities of shareholders of the real estate firm involved in the apartment building collapse on Saturday.

The apartment building in the "Lotus Riverside" compound of Minhang District collapsed entirely early Saturday, killing one worker who had gone into the building to fetch his tools.

The probe followed media reports saying some shareholders of Shanghai Meidu Real Estate are government officials.

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The property development company was run by the Meilong township between 1995 and 2001 and became a private company in 2001, official data showed.

Que Jinde, former chairman of the company, is assistant chief of the township government and holds a 15 percent stake in the company. Some other shareholders also work in the township government agencies.

Examination of the building's foundation and structure will be finished Thursday, according to the Minhang district information office.

More than 380 homeowners have demanded refunds or compensation by 5 pm Tuesday and the district government has pledged to protect the legitimate rights and interests of the owners.

The developer had been banned to sell housing following the collapse. It had sold out 489 of 629 homes.

The municipal government Tuesday ordered a sweeping quality inspection of buildings and infrastructures under construction in Shanghai.