Hawaii remained in the crosshairs of a potentially destructive tsunami this morning after a massive 8.9-magnitude quake hit off Honshu, Japan.

While the first waves weren’t expected to hit the islands until 3:07 a.m., scientists warned that the series of waves could last for hours.

Civil Defense ordered the evacuation of coastal inundation zones and the state opened emergency "refuge" centers.

John Cummings, a spokesman for city Department of Emergency Management, said about 30,000 residents live in the coastal inundation zone, according to recent estimates.

Even before Civil Defense sirens began sounding just before 10 p.m., Honolulu motorists began lining up at gas stations to top off their tanks. Police dispatch reported arguments over gas in Ewa Beach and many stations had long lines.

The Pacific Tsunami Warning Center, based in Ewa Beach, issued a tsunami watch at 7:56 p.m. after the quake struck 231 miles northeast of Tokyo. The watch was upgraded to a more serious warning about 9:30 p.m.

"A tsunami has been generated that could cause damage along coastlines of all islands in the state of Hawaii," the warning center said in a statement. "Urgent action should be taken to protect lives and property."

The warning center said wave heights could not be predicted, but the first wave may not be the largest. The warning center said "all shores are at risk" in Hawaii no matter which direction they face.

Chip McCreery, director of the warning center, said the latest forecast models show "wave amplitudes of up to 2 meters (6 feet) beyond normal sea levels in Hawaii.

"What these waves look like is an elevation of sea level, where the sea level will rise above its normal level and stay high for 10 or 15 minutes before they recede," McCreery said.

Because of the long length of tsunami waves, "they wrap around our islands very efficiently" so there is no point of impact that may see higher waves than other areas.

Because of the direction of the waves, the first major island hit would be Kauai, he said. It would only take 20 minutes for the first waves to move through the entire island chain, he said.

The city opened its Emergency Operations Center at the Frank F. Fasi building, where police, firefighters and Mayor Peter Carlisle assembled.

"We’re looking at a potentially very serious event here," said Cummings.

Hawaiian Electric has opened its emergency command center and is implementing its tsunami plans, according to Peter Rosegg, HECO spokesman.

The striking IBEW union workers are still out, Rosegg said, adding that the electric company has an agreement with the union that workers will return to work in case of a "major emergency."

Crews of Pearl Harbor ships were summoned, but the vessels will remain in the harbor, the Navy said.