OSAKA -- A rail maintenance train derailed at Nishi-Tanabe Station on the Osaka Midosuji Line early Thursday, affecting some 280,000 commuters, subway officials said.

The first car of the five-car work train derailed at the Abeno Ward station at around 3:45 a.m., halting electricity transmission along the line and delaying the start of the city-run subway's operations for four hours, the officials said.

None of the 14 workers on the maintenance train was injured.

Subway services between Senri-Chuo and Nakamozu stations did not start until around 9 a.m., the officials said, adding that the subway operator is investigating to determine the cause of the accident.