A small electrical fire broke out at the Kapolei rail station this morning, more than a month after the Honolulu Authority for Rapid Transportation announced its final round of testing.

A cable that monitored “stray current” from the third rail during testing caught fire on the guideway between the East Kapolei and West Oahu rail stations, HART executive director Lori Kahikina said in a press release.

The contractor, Hitachi Rail Honolulu, extinguished the fire before Honolulu Fire Department personnel arrived, Kahikina said in the statement.

Nine HFD units responded, the department said.

HART is investigating what might have caused the fire, and Hitachi Rail Honolulu will make any changes that the investigation finds necessary, Kahikina said in the statement.