Five people are missing after a fishing boat capsized near Couverden Point, Alaska, according to the U.S. Coast Guard.

The 50-foot fishing boat sent out a mayday call at 12:10 a.m. Sunday, the Coast Guard said.

The AMHS Hubbard overheard the broadcast and offered to assist, arriving on the scene first.

Evidence of the fishing boat was discovered, indicating a capsize, the Coast Guard said, but there has been no sign yet of those who were onboard.

Good Samaritans operating the ferry vessel have continued to aid the Coast Guard in its search efforts.

The Coast Guard said that it also received an emergency position-indicating radio beacon alert that was registered to the vessel. The signal originated just south of Point Couverden in Icy Strait.

People familiar with those aboard told officials that there were five people on the vessel. The number remains unconfirmed and could change, officials noted.

A search is now underway amid heavy snow and high winds.

It includes both water- and air-based missions, the later of which is led by a helicopter search team.

Winds are up to 60 mph in the area, while sea swells have reached 6 feet.

The Coast Guard said they are searching in "very rough conditions." However, there is not yet any indication of when the search might be called off or conclude.