More than 1 billion yuan ($163 million) has been misused during the construction of three subway lines in Nanjing, East China’s Jiangsu province, the city’s audit department said.

The department said that the contractors of the three subway lines, which total 62 km and cost 25.3 billion yuan, were paid 1.05 billion yuan more than they should have been.

Problems such as violations of bidding regulations and construction work without first signing a contract were also found in the audit.

The audit department has ordered the subway company and the contractors to correct the problems.