Five people remain missing after a military helicopter plunged into waters off Taiwan's southeast coast on Monday, said a spokesman with Taiwan's Chiayi Air Base.

The S-70C helicopter was on a mission to rescue an Indonesian fisherman suffering from angina when it disappeared from radar at 9:14 p.m., the spokesman said.

After it disappeared, rescuers were sent to waters located southeast of Orchid Island, an islet near southeast Taiwan's Taitung county. The rescuers saved one crew member after realizing the helicopter had crashed but could not find the other five.

The cause of the accident is still being investigated.