SINGAPORE, July 6 -- Singapore's Land Transport Authority (LTA) said on Wednesday that the defects found on trains manufactured by Kawasaki Heavy Industries and China Southern Railway (CSR) Sifang are "not safety-critical," after hairline cracks were found on the car-body of 26 trains delivered to SMRT, the major train operator of the city state.

In a statement, LTA said these defects were found during a check of new trains in late 2013, which are not structural cracks and not safety-critical.

"They don't affect the train's systems, performance or passengers' safety." LTA added. As the train are still under the manufacturer's warranty, LTA decided to send them back for rectification.

To further clarity on the safety of the trains, LTA said that it has conducted monthly safety assessments before the trains are put into use. Furthermore, an external third party assessment was also commissioned in 2013, which had confirmed that "the trains are safe to operate."

Previous media reports noted that repair of the defective trains will take seven years to complete. In the statement, LTA also clarified that the rectification work will be wrapped up in 2019.

In 2009, LTA awarded a 368 million Singapore-dollar (273 million U.S. dollars) contract to Kawasaki Heavy Industries and CSR Sifang for 22 trains. Last year, the authority signed for an additional 12 new trains. Most of the trains were to have been delivered between 2011 and 2012.