Bow of sunken tug on bottom left of US Coast Guard photo

Supply vessel sinks in Alaska
Crew safe, cause of sinking unknown...

A platform supply tug has sank during operations at an Alaskan oil platform Thursday morning.

The vessel, MONARCH, is operated by Kirkland-based firm Ocean Marine Services Inc. She was built in 1970.

It is unclear what happened to the vessel or what caused the sinking, but all crew are reported to have come off safely. The incident happened at the Granite Point oil platform in the north section of Cook Inlet 45 miles southwest of Anchorage, Alaska

The vessel was transporting six stainless steel totes, three plastic drums and eight steel drums containing various lube oils and chemicals. The chemicals are hazardous and mildly toxic, the US Coast Guard said in a statement.

The Chief Engineer of MONARCH was treated for contact with diesel fuel and exhaust inhalation.

Coast Guard assets, industry tugs, and dive personnel are enroute said the Coast Guard and that they are currently investigating the cause of the mishap.

The vessel reported taking on water at approximatley 5:51 a.m. Thursday and by noon had completely submerged. In the photo the bow of the vessel is all that is visible in the icy waters.