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Authorities in China's Shaanxi Province have issued an emergency notice calling a halt to the use of substandard steel bars at construction sites, which pose grave structural hazards to the buildings, Xinhuanet.com reported Wednesday.

Some construction sites in the province were found to be using cold-drawn steel bars that fall below the national mandatory standards in their cross-sectional area and mechanical properties. The reinforcement rate and ductility of these steel bars were reduced while their brittleness was heightened.

Steel bars from unknown sources or recycled from dismantled buildings were also found to be in use, the provincial housing and urban-rural development department said in a notice posted on its official website.

The notice stipulates that steel bars must undergo standard examination before they are allowed to be used at construction sites. The construction companies must process the steel bars onsite, instead of subcontracting the work to offsite plants.

The report came the same day when authorities in Hefei City, capital of Anhui Province, banned the use of bamboo sticks to replace steel wire or steel bars in producing precast concrete blocks.

The local construction quality safety supervision station on Tuesday afternoon found the problematic blocks were used at two apartment building sites. The blocks were destroyed on spot and the builders were told to rectify their practice.

The bamboo-stick concrete blocks, which are used to fix the position of reinforcing bars in concrete structures, can be easily broken by hand, according to Wei Bangren, the deputy director of the station.

While there is currently no national standard regulating the concrete blocks, the use of inferior material to save costs is not to be tolerated, the station said in the notice.